Exploring the Synthetic Potential of γ-Lactam Derivatives Obtained from a Multicomponent Reaction—Applications as Antiproliferative Agents

Ci a ion: López-F ancés, A.; del
Co e, X.; Se na-Bu gos, Z.; Ma ínez
de Ma igo a, E.; Palacios, F.; Vica io,
J. Explo ing he Syn he ic Po en ial o
γ-Lac am De i a i es Ob ained om
a Mul icomponen Reac ion—
Applica ions as An ip oli e a i e
Agen s. Molecules 2022,27, 3624.
h ps://doi.o g/10.3390/
molecules27113624
Academic Edi o s: Sobhi M. Gomha
and Mahe Fa halla
Recei ed: 18 May 2022
Accep ed: 1 June 2022
Published: 5 June 2022
Publishe ’s No e: MDPI s ays neu al
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molecules
A icle
Explo ing he Syn he ic Po en ial o γ-Lac am De i a i es
Ob ained om a Mul icomponen Reac ion—Applica ions as
An ip oli e a i e Agen s
Ad ián López-F ancés , Xabie del Co e , Zu iñe Se na-Bu gos, Edo a Ma ínez de Ma igo a ,
F ancisco Palacios * and Ja ie Vica io *
Depa amen o de Química O gánica I, Cen o de In es igación y Es udios A anzados “Lucio Lasca ay”,
Facul ad de Fa macia, Uni e si y o he Basque Coun y, UPV/EHU Paseo de la Uni e sidad 7,
01006 Vi o ia-Gas eiz, Spain; [email p o ec ed] (A.L.-F.); xabie [email p o ec ed] (X.d.C.);
[email p o ec ed] (Z.S.-B.); [email p o ec ed] (E.M.d.M.)
*Co espondence: [email p o ec ed] (F.P.); ja ie [email p o ec ed] (J.V.);
Tel.: +34-945013103 (F.P.); +34-945013087 (J.V.)
Abs ac :
A s udy on he eac i i y o 3-amino
α
,
β
-unsa u a ed
γ
-lac am de i a i es ob ained om a
mul icomponen eac ion is p esen ed. Key ea u es o he subs a es a e he p esence o an endocyclic
α
,
β
-unsa u a ed amide moie y and an enamine unc ionali y. Following di e en syn he ic p o ocols,
he unc ionaliza ion a h ee di e en posi ions o he lac am co e is achie ed. In he p esence o
a so base, unde he modynamic condi ions, he unc ionaliza ion a C-4 akes place whe e he
subs a es beha e as enamines, while he use o a s ong base, unde kine ic condi ions, leads o
he o ma ion o C-5- unc ionalized
γ
-lac ams, in he p esence o e hyl glyoxala e, h ough a highly
dias e eoselec i e inylogous aldol eac ion. Mo eo e , he nucleophilic addi ion o o ganome allic
species allows he unc ionaliza ion a C-3, h ough he imine au ome , a o ding
γ
-lac ams bea ing
e asubs i u ed s e eocen e s, whe e he subs a es ac as imine elec ophiles. Taking in o accoun
he ad an age o he p esence o a chi al s e eocen e in C-5 subs i u ed
γ
-lac ams, u he dias e eos-
elec i e ans o ma ions a e also explo ed, leading o no el bicyclic subs a es holding a used
γ
and
δ
-lac am skele on. Rema kably, an example o a highly s e eoselec i e o mal [3+3] cycloaddi ion
eac ion o chi al
γ
-lac am subs a es is epo ed o he syn hesis o 1,4-dihid opy idines, whe e
a non-co alen a ac i e in e ac ion o a ca bonyl g oup wi h an elec on-de icien a ene seems o
d i e he s e eoselec i i y o he eac ion o he exclusi e o ma ion o he cis isome . In o de o
unambiguously de e mine he subs i u ion pa e n esul ing om he di e se eac ions, an ex ensi e
cha ac e iza ion o he subs a es is de ailed h ough 2D NMR and/o X- ay expe imen s. Likewise,
applica ions o he subs a es as an ip oli e a i e agen s agains lung and o a ian cance cells a e
also desc ibed.
Keywo ds:
mul icomponen syn hesis;
γ
-lac ams; egioselec i e unc ionaliza ion; an ip oli e a i e e ec
1. In oduc ion
Among he e ocyclic compounds, he
γ
-lac am ing is a p i ileged sca old ha ap-
pea s as a ele an cons uc ion mo i o he de elopmen o new d ugs. A wide ange
o bioac i e na u al p oduc s o clinically used d ugs and pha maceu icals embody he
γ
-lac am sca old as a pa o hei complex molecula a chi ec u e [
1
,
2
]. Thus, emen-
dous e o s ha e been de o ed du ing he las decades owa ds he e icien syn hesis
o unc ionalized
γ
-lac am de i a i es [
3
–
7
]. In pa icula , 3-py olin-2-ones (also named
as 1,5-dihyd opy ol-2-ones), closely ela ed o
γ
-lac ams, a e no only use ul building
blocks in chemical syn hesis [
8
,
9
], bu also co e s uc u es o bioac i e na u al p oduc s and
pha maceu icals [10–16].
Molecules 2022,27, 3624. h ps://doi.o g/10.3390/molecules27113624 h ps://www.mdpi.com/jou nal/molecules
Molecules 2022,27, 3624 2 o 25
A s aigh o wa d me hod o he syn hesis o 3-py olin-2-ones consis s o a h ee-
componen eac ion whe e ei he py u a e [
17
–
20
] o ace ylene ca boxyla e [
21
–
25
] de i a-
i es a e mixed wi h aldehydes and amines, in he p esence o a B öns ed acid ca alys ,
leading o enol-con aining iso- e onic acid s uc u es o hei enamine subs a es, 3-amino
3-py olin-2-ones. Those mul icomponen p o ocols [
26
,
27
] a e conside ed o be essen-
ial syn he ic ools in di e si y-o ien ed syn hesis [
28
,
29
]. 3-amino 3-py olin-2-ones a e
indeed cyclic
α
-dehyd o
α
-amino acids and such a skele on is ound widely dis ibu ed
among many biologically ac i e compounds [
28
–
34
]. In addi ion, many bioac i e na u al
p oduc s a e based in a α,β-unsa u a ed γ-lac am s uc u e, such as cy o oxic polyke ides
Mycelio he mophins E, C, and D [
35
], cy o oxic Pukeleumid E p esen in Lyngbya majuscule
algae [
36
], HIV-in eg ase inhibi o O e omicyn [
37
,
38
], and an ibio ic Py ocidine A [
39
],
bo h o hem isola ed om di e en ungus, and in he basic s uc u e o 1,2-di hiole g oup
an ibio ics (Holo hin, Holomycin, Thiolu in, and Au eo h icin) [40] (Figu e 1).
Molecules 2022, 27, x FOR PEER REVIEW 2 o 26
and pha maceu icals [10–16].
A s aigh o wa d me hod o he syn hesis o 3-py olin-2-ones consis s o a
h ee-componen eac ion whe e ei he py u a e [17–20] o ace ylene ca boxyla e [21–25]
de i a i es a e mixed wi h aldehydes and amines, in he p esence o a B öns ed acid
ca alys , leading o enol-con aining iso- e onic acid s uc u es o hei enamine sub-
s a es, 3-amino 3-py olin-2-ones. Those mul icomponen p o ocols [26,27] a e consid-
e ed o be essen ial syn he ic ools in di e si y-o ien ed syn hesis [28,29]. 3-amino
3-py olin-2-ones a e indeed cyclic α-dehyd o α-amino acids and such a skele on is
ound widely dis ibu ed among many biologically ac i e compounds [28–34]. In addi-
ion, many bioac i e na u al p oduc s a e based in a α,β-unsa u a ed γ-lac am s uc u e,
such as cy o oxic polyke ides Mycelio he mophins E, C, and D [35], cy o oxic
Pukeleumid E p esen in Lyngbya majuscule algae [36], HIV-in eg ase inhibi o O e omi-
cyn [37,38], and an ibio ic Py ocidine A [39], bo h o hem isola ed om di e en un-
gus, and in he basic s uc u e o 1,2-di hiole g oup an ibio ics (Holo hin, Holomycin,
Thiolu in, and Au eo h icin) [40] (Figu e 1).
Figu e 1. Bioac i e na u al 1,5-dihyd opy ol-2-ones (* deno es acemic).
In addi ion, om a syn he ic poin o iew, 3-amino 3-py olin-2-ones a e cyclic
enamine subs a es and, he e o e, hey a e ou s anding ools in chemical syn hesis [41].
In e es ingly, some py olone-based sys ems ha e been iden i ied as p53−MDM2 [42]
and STAT3 [43] inhibi o s, which esul in s ong an ip oli e a i e ac i i y, and, in addi-
ion, many o he molecules con aining he py olone sca old ha e been desc ibed as e -
icien an i umo al agen s [44–48].
A ew yea s ago, we epo ed a B öns ed-acid-ca alyzed enan ioselec i e syn hesis
o 3-amino 3-py olin-2-ones h ough a mul icomponen eac ion, making use o amines,
aldehydes, and py u a e de i a i es as s a ing ma e ials [24]. Mo e ecen ly, we ha e
ex ended his s a egy o he p epa a ion o he co esponding phospho us and luo-
ine-con aining analogs, using in his case luo ine and/o phosphona e-subs i u ed al-
dehydes and py u a es [25]. Rema kably, many o hose molecules ha e shown s ong
an ip oli e a i e ac i i y, inhibi ing he g ow h o se e al ca cinoma human umo cell
lines h ough he ac i a ion o he apop o ic mechanism [10,11]. Key ea u es o he
s uc u e o hose subs a es a e he e y eac i e cyclic enamine moie y and he p esence
o a chi al s e eocen e a he 5-membe ed ing. Taking he ad an age o hose wo cha -
ac e is ics, we ha e used 3-amino 3-py olin-2-ones as subs a es in Lewis-acid-ca alyzed
o mal [3+3] annula ion eac ions, o he p epa a ion o bicyclic 1,4-dihid opy idines
wi h a ema kably high deg ee o s e eoselec i i y [12]. Conside ing he easiness o he
Figu e 1. Bioac i e na u al 1,5-dihyd opy ol-2-ones (* deno es acemic).
In addi ion, om a syn he ic poin o iew, 3-amino 3-py olin-2-ones a e cyclic
enamine subs a es and, he e o e, hey a e ou s anding ools in chemical syn hesis [
41
].
In e es ingly, some py olone-based sys ems ha e been iden i ied as p53
−
MDM2 [
42
] and
STAT3 [
43
] inhibi o s, which esul in s ong an ip oli e a i e ac i i y, and, in addi ion,
many o he molecules con aining he py olone sca old ha e been desc ibed as e icien
an i umo al agen s [44–48].
A ew yea s ago, we epo ed a B öns ed-acid-ca alyzed enan ioselec i e syn hesis
o 3-amino 3-py olin-2-ones h ough a mul icomponen eac ion, making use o amines,
aldehydes, and py u a e de i a i es as s a ing ma e ials [
24
]. Mo e ecen ly, we ha e
ex ended his s a egy o he p epa a ion o he co esponding phospho us and luo ine-
con aining analogs, using in his case luo ine and/o phosphona e-subs i u ed aldehydes
and py u a es [
25
]. Rema kably, many o hose molecules ha e shown s ong an ip oli e a-
i e ac i i y, inhibi ing he g ow h o se e al ca cinoma human umo cell lines h ough he
ac i a ion o he apop o ic mechanism [
10
,
11
]. Key ea u es o he s uc u e o hose sub-
s a es a e he e y eac i e cyclic enamine moie y and he p esence o a chi al s e eocen e
a he 5-membe ed ing. Taking he ad an age o hose wo cha ac e is ics, we ha e used
3-amino 3-py olin-2-ones as subs a es in Lewis-acid-ca alyzed o mal [3+3] annula ion e-
ac ions, o he p epa a ion o bicyclic 1,4-dihid opy idines wi h a ema kably high deg ee
o s e eoselec i i y [
12
]. Conside ing he easiness o he mul icomponen p epa a ion o
3-amino 3-py olin-2-ones and hei syn he ic po en ial in o ganic syn hesis, we hough
ha a s udy on he syn he ic applica ions o such lac am subs a es would be o g ea
in e es in he ield. Taking in o accoun all he conside a ions men ioned abo e, he e we
Molecules 2022,27, 3624 3 o 25
epo he syn he ic applica ions o enamine-de i ed
γ
-lac am de i a i es, ob ained om a
simple mul icomponen eac ion, wi h a special ocus on s e eoselec i e ans o ma ions.
Mo eo e , in iew o he ele ance o he
γ
-lac am co e in biological sys ems and hei
demons a ed p ope ies as an i umo al agen s, a s udy o hei an ip oli e a i e ac i i y
agains ca cinomic human o a ian and al eola basal epi helial cells is also p esen ed.
2. Resul s and Discussion
2.1. Chemis y
As p e iously desc ibed [
9
,
21
], he mul icomponen eac ion be ween a oma ic amines
1
, aldehydes
2
, and py u a e de i a i es
3
, in he p esence o a ca aly ic amoun o BINOL-
de i ed phospho ic acid, p oceeds smoo hly in a ew hou s o yield he a ge 3-amino
3-py olin-2-ones 4–5(Scheme 1).
Molecules 2022, 27, 3624 3 o 27
Lewis-acid-ca alyzed o mal [3+3] annula ion eac ions, o he p epa a ion o bicyclic
1,4-dihid opy idines wi h a ema kably high deg ee o s e eoselec i i y [12]. Conside ing
he easiness o he mul icomponen p epa a ion o 3-amino 3-py olin-2-ones and hei
syn he ic po en ial in o ganic syn hesis, we hough ha a s udy on he syn he ic
applica ions o such lac am subs a es would be o g ea in e es in he ield. Taking in o
accoun all he conside a ions men ioned abo e, he e we epo he syn he ic applica ions
o enamine-de i ed γ-lac am de i a i es, ob ained om a simple mul icomponen
eac ion, wi h a special ocus on s e eoselec i e ans o ma ions. Mo eo e , in iew o he
ele ance o he γ-lac am co e in biological sys ems and hei demons a ed p ope ies as
an i umo al agen s, a s udy o hei an ip oli e a i e ac i i y agains ca cinomic human
o a ian and al eola basal epi helial cells is also p esen ed.
2. Resul s and Discussion
2.1. Chemis y
As p e iously desc ibed [9,21], he mul icomponen eac ion be ween a oma ic
amines 1, aldehydes 2, and py u a e de i a i es 3, in he p esence o a ca aly ic amoun
o BINOL-de i ed phospho ic acid, p oceeds smoo hly in a ew hou s o yield he a ge
3-amino 3-py olin-2-ones 4-5 (Scheme 1)
Scheme 1. MCR o he syn hesis o γ-lac ams 4-5.
Following his p ocedu e, se e al 3-amino 3-py olin-2-ones 4,5 we e syn hesized
and hei eac i i y was explo ed in di e se eac ions. As has been add essed abo e,
3-amino 3-py olin-2-ones de i a i es 4 and 5 con ain he enamine moie y in hei
s uc u e. In iew o he po en ial nucleophilic cha ac e o hose subs a es, i s we
es ed he eac i i y o he enamine unc ionali y as a nucleophile using i s he mos
simple γ-lac am subs a es de i ed om e hyl py u a e and o maldehyde 4a,b (Scheme
2). The conjuga e addi ion o he cyclic enamines 4 o ace ylene ca boxyla es 6 (R2 = OAlk)
can be pe o med by he gene a ion o he aza-enola e h ough an ini ial ea men wi h
LDA a low empe a u e, ollowed by he addi ion o he elec ophile. The eac ion
p oceeds wi h a high deg ee o egioselec i i y a he posi ion C-4 o he i e-membe ed
he e ocycle. Following his p ocedu e, he unc ionaliza ion eac ion was success ully
applied o me hyl, e hyl, e -bu yl, and 2-naph hyl ca boxyla e de i a i es 7a– in
excellen yields (Scheme 2).
Unde he same eac ion condi ions, he conjuga e addi ion o γ-lac ams 4 o ace yl
ace ylene (R2 = CH3) ailed o gi e he nucleophilic addi ion de i a i es. Howe e , he
new se o eac ion condi ions such as s oichiome ic amoun s o a Lewis acid Yb(OT )3
led o he o ma ion o unc ionalized lac ams 7g–h in excellen yields (Scheme 2).
γ-Lac ams 7 we e ully cha ac e ized on he basis o hei 1H and 13C NMR and IR
spec um and HRMS. Func ionalized γ-lac am 7a was selec ed in o de o
unambiguously es ablish he s uc u e o he eac ion p oduc s ob ained om he
conjuga e addi ion o ac i a ed alkynes. The unc ionaliza ion a C-4 is e iden by he
p esence o a single a δH = 4.41 ppm in 1H NMR spec um ha in eg a es o wo p o ons,
co esponding o he me hylene g oup a he 5-membe ed ing and he wo double s a δH
= 7.56 and 5.63 ppm o he alkene g oup wi h a ypical coupling cons an o a ans
con igu a ion o he C=C double bond (3JHH = 15.7 Hz). As expec ed, bo h p o ons a he
Scheme 1. MCR o he syn hesis o γ-lac ams 4–5.
Following his p ocedu e, se e al 3-amino 3-py olin-2-ones
4
,
5
we e syn hesized and
hei eac i i y was explo ed in di e se eac ions. As has been add essed abo e, 3-amino
3-py olin-2-ones de i a i es
4
and
5
con ain he enamine moie y in hei s uc u e. In iew
o he po en ial nucleophilic cha ac e o hose subs a es, i s we es ed he eac i i y o
he enamine unc ionali y as a nucleophile using i s he mos simple
γ
-lac am subs a es
de i ed om e hyl py u a e and o maldehyde
4a
,
b
(Scheme 2). The conjuga e addi ion
o he cyclic enamines
4
o ace ylene ca boxyla es
6
(R
2
= OAlk) can be pe o med by he
gene a ion o he aza-enola e h ough an ini ial ea men wi h LDA a low empe a u e,
ollowed by he addi ion o he elec ophile. The eac ion p oceeds wi h a high deg ee
o egioselec i i y a he posi ion C-4 o he i e-membe ed he e ocycle. Following his
p ocedu e, he unc ionaliza ion eac ion was success ully applied o me hyl, e hyl, e -
bu yl, and 2-naph hyl ca boxyla e de i a i es 7a– in excellen yields (Scheme 2).
Unde he same eac ion condi ions, he conjuga e addi ion o
γ
-lac ams
4
o ace yl
ace ylene (R
2
= CH
3
) ailed o gi e he nucleophilic addi ion de i a i es. Howe e , he
new se o eac ion condi ions such as s oichiome ic amoun s o a Lewis acid Yb(OT )
3
led
o he o ma ion o unc ionalized lac ams 7g–hin excellen yields (Scheme 2).
γ
-Lac ams
7
we e ully cha ac e ized on he basis o hei
1
H and
13
C NMR and IR
spec um and HRMS. Func ionalized
γ
-lac am
7a
was selec ed in o de o unambiguously
es ablish he s uc u e o he eac ion p oduc s ob ained om he conjuga e addi ion o
ac i a ed alkynes. The unc ionaliza ion a C-4 is e iden by he p esence o a single a
δH
= 4.41 ppm in
1
H NMR spec um ha in eg a es o wo p o ons, co esponding o he
me hylene g oup a he 5-membe ed ing and he wo double s a
δH
= 7.56 and 5.63 ppm
o he alkene g oup wi h a ypical coupling cons an o a ans con igu a ion o he C=C
double bond (
3
J
HH
= 15.7 Hz). As expec ed, bo h p o ons a he alkene bond p o ed o
be coupled oge he in he homonuclea co ela ion spec oscopy (COSY) spec um. In
addi ion, he
13
C NMR spec um shows a signal a
δC
= 49.2 ppm which was assigned o a
CH
2
ca bon by dis o ionless enhancemen by pola iza ion ans e (DEPT) expe imen s.
The p o on and ca bon signals assigned o he me hylene g oup show a co ela ion in
he he e onuclea single quan um cohe ence spec oscopy (HSQC) spec um. Mo eo e ,
some o he cha ac e is ic ea u es o he
13
C NMR spec um o
6a
a e he wo signals
co esponding o he wo enamine qua e na y ca bons (DEPT) a
δC
= 136.6 and 107.5 ppm
as well as he signals co esponding o he me hine ca bons (DEPT) o he alkene g oup a
δC= 135.5 and 113.2 ppm.
Molecules 2022,27, 3624 4 o 25
Molecules 2022, 27, x FOR PEER REVIEW 4 o 26
g oup show a co ela ion in he he e onuclea single quan um cohe ence spec oscopy
(HSQC) spec um. Mo eo e , some o he cha ac e is ic ea u es o he 13C NMR spec um
o 6a a e he wo signals co esponding o he wo enamine qua e na y ca bons (DEPT) a
δC = 136.6 and 107.5 ppm as well as he signals co esponding o he me hine ca bons
(DEPT) o he alkene g oup a δC = 135.5 and 113.2 ppm.
Scheme 2. Func ionaliza ion o unsubs i u ed γ-lac ams 4a,b. Reac ion condi ions: (a) LDA (1.1
equi .), THF, −78 °C hen HC≡C–CO2R (1.1 equi .), −78 °C o . (b) Yb(OT )3 (1.1 equi .), HC≡C–
COCH3 (1.1 equi .), CH2Cl2, .
In cong ui y wi h he p oposed s uc u e, he he e onuclea mul iple bond co ela-
ion spec oscopy (HMBC) spec um o 6a p esen s wo clea co ela ions o he me h-
ylene p o ons a he he e ocycle wi h he wo enamine ca bons, as well as a hi d one
wi h he alkene ca bon nex o he γ-lac am ing a δC = 135.5 ppm. As expec ed, he less
shielded signal o he ole inic p o ons a δH = 7.56 ppm, co esponding o he me hine
g oup nex o he he e ocycle, shows co ela ion wi h he wo enamine ca bons and he
me hylene g oup a he 5-membe ed ing, as well as wi h he second ca bon o he alkene
moie y a δC = 113.2 ppm and he ca bonyl o he e y conjuga ed es e g oup a δC = 165.6
ppm. The mos shielded signal o he ole inic p o ons a δH = 5.63 ppm, assigned o he
CH g oup nex o he ca boxyl g oup, shows a ela ionship wi h he ca boxyl g oup and
he o he ca bon o he alkene moie y a δC = 135.5 ppm. Mo eo e , his ole inic p o on
only shows co ela ion wi h one o he qua e na y enamine ca bons a δC = 107.5 ppm.
In o de o ex end u he he syn he ic applica ions o γ-lac am subs a es, nex we
explo ed he eac i i y o he di e en unc ionalized de i a i es 7. Ou i s a emp o
p omo e an in amolecula cycliza ion om ac yla e subs i u ed γ-lac am 7a unde basic
condi ions ailed, which was a ibu ed o an un a o able ans con igu a ion o he al-
kene bond. Fo his eason, nex , we pe o med he double educ ion o he alkene and
enamine moie ies unde hyd ogen p essu e in he p esence o palladium as he ca alys ,
a o ding sa u a ed γ-lac am de i a i e 8 in excellen yield wi h a comple e deg ee o
Scheme 2.
Func ionaliza ion o unsubs i u ed
γ
-lac ams
4a
,
b
. Reac ion condi ions: (a) LDA
(1.1 equi .), THF,
−
78
◦
C hen HC
≡
C–CO
2
R (1.1 equi .),
−
78
◦
C o . (b) Yb(OT )
3
(1.1 equi .),
HC≡C–COCH3(1.1 equi .), CH2Cl2, .
In cong ui y wi h he p oposed s uc u e, he he e onuclea mul iple bond co ela ion
spec oscopy (HMBC) spec um o
6a
p esen s wo clea co ela ions o he me hylene
p o ons a he he e ocycle wi h he wo enamine ca bons, as well as a hi d one wi h he
alkene ca bon nex o he
γ
-lac am ing a
δC
= 135.5 ppm. As expec ed, he less shielded
signal o he ole inic p o ons a
δH
= 7.56 ppm, co esponding o he me hine g oup nex
o he he e ocycle, shows co ela ion wi h he wo enamine ca bons and he me hylene
g oup a he 5-membe ed ing, as well as wi h he second ca bon o he alkene moie y a
δC= 113.2 ppm
and he ca bonyl o he e y conjuga ed es e g oup a
δC
= 165.6 ppm. The
mos shielded signal o he ole inic p o ons a
δH
= 5.63 ppm, assigned o he CH g oup
nex o he ca boxyl g oup, shows a ela ionship wi h he ca boxyl g oup and he o he
ca bon o he alkene moie y a
δC
= 135.5 ppm. Mo eo e , his ole inic p o on only shows
co ela ion wi h one o he qua e na y enamine ca bons a δC= 107.5 ppm.
In o de o ex end u he he syn he ic applica ions o
γ
-lac am subs a es, nex we
explo ed he eac i i y o he di e en unc ionalized de i a i es
7
. Ou i s a emp
o p omo e an in amolecula cycliza ion om ac yla e subs i u ed
γ
-lac am
7a
unde
basic condi ions ailed, which was a ibu ed o an un a o able ans con igu a ion o he
alkene bond. Fo his eason, nex , we pe o med he double educ ion o he alkene and
enamine moie ies unde hyd ogen p essu e in he p esence o palladium as he ca alys ,
a o ding sa u a ed
γ
-lac am de i a i e
8
in excellen yield wi h a comple e deg ee o
syn-dias e eoselec ion (Scheme 3). As a consequence o he less s ained s uc u e ob ained
in he sa u a ed de i a i e
8
, in his case he ea men unde basic condi ions leads o
he o ma ion o bicyclic
γ
-lac am
9
in almos quan i a i e yield (Scheme 3). As a as we
a e conce ned, his ep esen s he i s example o a syn he ic me hodology leading o he
dias e eoselec i e o ma ion o a bicyclic subs a e comp ising bo h
γ
and
δ
-lac am uni s.
Molecules 2022,27, 3624 5 o 25
Addi ionally, he selec i e hyd olysis o he enamine moie y can be pe o med unde acidic
condi ions o yield iso e amic acid de i a i e 10 in an almos quan i a i e yield.
Molecules 2022, 27, x FOR PEER REVIEW 5 o 26
syn-dias e eoselec ion (Scheme 3). As a consequence o he less s ained s uc u e ob-
ained in he sa u a ed de i a i e 8, in his case he ea men unde basic condi ions
leads o he o ma ion o bicyclic γ-lac am 9 in almos quan i a i e yield (Scheme 3). As
a as we a e conce ned, his ep esen s he i s example o a syn he ic me hodology
leading o he dias e eoselec i e o ma ion o a bicyclic subs a e comp ising bo h γ and
δ-lac am uni s. Addi ionally, he selec i e hyd olysis o he enamine moie y can be pe -
o med unde acidic condi ions o yield iso e amic acid de i a i e 10 in an almos
quan i a i e yield
N
H
p-Tol
N
O
7a
p-Tol
OMe
O
N
H
p-Tol
N
O
8(92%)
p-Tol
OMe
O
N
N
O
9(98%)
p-Tol
p-Tol
O
OH
N
O
10 (96%)
p-Tol
OMe
O
H2(80 psi), Pd-C (10 %mol)
E OH,
NaH
Toluene 110ºC
aq. HCl
THF, 66ºC
Scheme 3. Syn he ic applica ions o unc ionalized γ-lac am 7a.
The ela i e con igu a ion o he s e eocen e s in γ-lac ams 8 and 9 was de e mined
by nuclea O e hause enhancemen spec oscopy (NOESY) expe imen s (see ESI). NMR
expe imen s wi h compound 8 showed a NOE o 3.98% be ween bo h p o ons a he wo
s e eogenic cen e s, a δ = 4.13 and 2.91 ppm, espec i ely, indica ing ha hese wo a -
oms a e o ien ed in he same di ec ion. This ela i e con igu a ion is in ag eemen wi h
he accep ed mechanism o ca aly ic hyd ogena ion o a ca bon-ca bon double bond,
consis ing in a syn addi ion o hyd ogen.
Con inuing wi h ou in e es in he nucleophilic addi ion eac ions o
enamine-de i ed γ-lac ams, nex , we explo ed he unc ionaliza ion o subs a es 4c,d,
holding a phospho a ed subs i uen a he posi ion 4 o he ing. Acco dingly, he ea -
men o γ-lac ams 4c,d wi h LDA a low empe a u e, ollowed by he addi ion o e hyl
glyoxala e, led o he nucleophilic addi ion p oduc s 12a,b, whe e he 5-membe ed ing is
selec i ely unc ionalized a C-5. In his case, he p esence o he bulky phosphona e o
phosphine oxide subs i uen s may block he β-enamine unc ionaliza ion and he eac-
ion p esumably p oceeds h ough he gene a ion o a oma ic enol- ype in e media e 11,
unde kine ic condi ions ins ead o he aza-enola e. Then, he subsequen selec i e i-
nylogous nucleophilic addi ion o anionic species 11 o he aldehyde elec ophile p o-
ceeds selec i ely a posi ion 5 o he 5-membe ed ing, leading o he o ma ion o
α-hyd oxyes e - unc ionalized γ-lac ams 12a,b in good yields (Scheme 4). I should be
no ed ha hese a e he i s examples o C-5- unc ionalized phospho us-subs i u ed
γ-lac ams holding an enamine s uc u e, since such subs a es a e known o apidly
p o ide he enol-de i ed γ-lac ams h ough he spon aneous hyd olysis o he enamine
moie y, as a consequence o he high s e ic hind ance p esen in he 5-membe ed he e -
ocycle [21].
Scheme 3. Syn he ic applica ions o unc ionalized γ-lac am 7a.
The ela i e con igu a ion o he s e eocen e s in
γ
-lac ams
8
and
9
was de e mined
by nuclea O e hause enhancemen spec oscopy (NOESY) expe imen s (see ESI). NMR
expe imen s wi h compound
8
showed a NOE o 3.98% be ween bo h p o ons a he
wo s e eogenic cen e s, a
δ
= 4.13 and 2.91 ppm, espec i ely, indica ing ha hese wo
a oms a e o ien ed in he same di ec ion. This ela i e con igu a ion is in ag eemen wi h
he accep ed mechanism o ca aly ic hyd ogena ion o a ca bon-ca bon double bond,
consis ing in a syn addi ion o hyd ogen.
Con inuing wi h ou in e es in he nucleophilic addi ion eac ions o enamine-de i ed
γ
-lac ams, nex , we explo ed he unc ionaliza ion o subs a es
4c
,
d
, holding a phospho -
a ed subs i uen a he posi ion 4 o he ing. Acco dingly, he ea men o
γ
-lac ams
4c
,
d
wi h LDA a low empe a u e, ollowed by he addi ion o e hyl glyoxala e, led o he nucle-
ophilic addi ion p oduc s
12a
,
b
, whe e he 5-membe ed ing is selec i ely unc ionalized a
C-5. In his case, he p esence o he bulky phosphona e o phosphine oxide subs i uen s
may block he
β
-enamine unc ionaliza ion and he eac ion p esumably p oceeds h ough
he gene a ion o a oma ic enol- ype in e media e
11
, unde kine ic condi ions ins ead o
he aza-enola e. Then, he subsequen selec i e inylogous nucleophilic addi ion o anionic
species
11
o he aldehyde elec ophile p oceeds selec i ely a posi ion 5 o he 5-membe ed
ing, leading o he o ma ion o
α
-hyd oxyes e - unc ionalized
γ
-lac ams
12a
,
b
in good
yields (Scheme 4). I should be no ed ha hese a e he i s examples o C-5- unc ionalized
phospho us-subs i u ed
γ
-lac ams holding an enamine s uc u e, since such subs a es a e
known o apidly p o ide he enol-de i ed
γ
-lac ams h ough he spon aneous hyd ol-
ysis o he enamine moie y, as a consequence o he high s e ic hind ance p esen in he
5-membe ed he e ocycle [21].
Molecules 2022, 27, x FOR PEER REVIEW 6 o 26
LDA
THF, −78ºC
N
H
p-Tol
N
O
p-Tol
N
H
p-Tol
N
O
p-Tol
OH
E O2C
N
H
p-Tol
N
O
p-Tol
4c: R = OE
4d: R = Ph
11
E O2C
O
PR2
O
PR2
O
PR2
O
−78 ºC o
12a: R = OE (61%)
12b: R = Ph (86%)
Scheme 4. S e eoselec i e nucleophilic addi ion o phospho a ed lac ams 4c,d o e hyl glyoxala e.
Rema kably, he nucleophilic addi ion eac ion p oceeds wi h a high deg ee o s e-
eoselec i i y and a single dias e eoisome is obse ed in he NMR spec a o he c ude
eac ion. Un o una ely, NOESY expe imen s on he unc ionalized γ-lac ams did no
p o ide solid e idence ha could lead o he unambiguous de e mina ion o he ela i e
con igu a ion o he adduc . Fo his eason, a single c ys al o subs a e 12b was isola ed
om a mix u e o CH
2
Cl
2
/hexanes and, nex , he s uc u e ob ained by X- ay di ac ion
expe imen s e ealed unequi ocally a ela i e con igu a ion de i ed om he an-
i-addi ion o he γ-lac am co e o he aldehyde elec ophile (Figu e 2). A plausible an-
si ion s a e leading o he an i-de i a i e may consis o an elec os a ic in e ac ion be-
ween he aldehyde and he li hium ca ion, di ec ing he ca bonyl g oup owa ds he
py ole ing. A possible addi ional s abiliza ion by hyd ogen bonding be ween he NH
subs i uen and he ca bonyl oxygen may p o ide a e y igid a angemen o he alde-
hyde, which o ien s i s e minal hyd ogen in a gauche con o ma ion ela i e o he bulky
phospho us subs i uen , as d awn in he Newman p ojec ion shown in Figu e 2.
Figu e 2. Plausible ansi ion s a e o he nucleophilic addi ion o e hyl glyoxala e and X- ay
s uc u e o unc ionalized γ-lac am 12b (H, whi e; C, g ey, O, ed, N, blue, P, pink) (R, R enan i-
ome shown).
Su p isingly, unde he same eac ion condi ions, o he special case o he nucle-
ophilic addi ion o phospho a ed γ-lac am 4d o p-ni ophenyl isocyana e, he in oduc-
ion o an imine moie y in o he i e-membe ed ing was obse ed o gi e γ-lac am 13
(Scheme 5). An explana ion o his beha io may consis o an ini ial o ma ion o he
amide 14 by he ypical nucleophilic addi ion o an isocyana e subs a e. Then, a spon-
aneous oxida ion o he 5-membe ed he e ocycle is p oposed o yield in e media e 15.
Nex , an in amolecula conjuga e addi ion o he amide ni ogen o he he e ocycle
would a o d he ins able h ee-membe ed azi idinone species 16, and a subsequen e-
a angemen o he azi idinone and he enamine moie ies a he γ-lac am co e would lead
o N- o mamide 17 ha unde goes a spon aneous clea age o he o myl esidue o a o d
imine- unc ionalized γ-lac am 13.
Scheme 4. S e eoselec i e nucleophilic addi ion o phospho a ed lac ams 4c,d o e hyl glyoxala e.
Rema kably, he nucleophilic addi ion eac ion p oceeds wi h a high deg ee o s e eos-
elec i i y and a single dias e eoisome is obse ed in he NMR spec a o he c ude eac ion.
Un o una ely, NOESY expe imen s on he unc ionalized
γ
-lac ams did no p o ide solid
e idence ha could lead o he unambiguous de e mina ion o he ela i e con igu a ion o

Molecules 2022,27, 3624 6 o 25
he adduc . Fo his eason, a single c ys al o subs a e
12b
was isola ed om a mix u e
o CH
2
Cl
2
/hexanes and, nex , he s uc u e ob ained by X- ay di ac ion expe imen s
e ealed unequi ocally a ela i e con igu a ion de i ed om he an i-addi ion o he
γ
-
lac am co e o he aldehyde elec ophile (Figu e 2). A plausible ansi ion s a e leading o
he an i-de i a i e may consis o an elec os a ic in e ac ion be ween he aldehyde and he
li hium ca ion, di ec ing he ca bonyl g oup owa ds he py ole ing. A possible addi ional
s abiliza ion by hyd ogen bonding be ween he NH subs i uen and he ca bonyl oxygen
may p o ide a e y igid a angemen o he aldehyde, which o ien s i s e minal hyd ogen
in a gauche con o ma ion ela i e o he bulky phospho us subs i uen , as d awn in he
Newman p ojec ion shown in Figu e 2.
Molecules 2022, 27, x FOR PEER REVIEW 6 o 26
Scheme 4. S e eoselec i e nucleophilic addi ion o phospho a ed lac ams 4c,d o e hyl glyoxala e.
Rema kably, he nucleophilic addi ion eac ion p oceeds wi h a high deg ee o s e-
eoselec i i y and a single dias e eoisome is obse ed in he NMR spec a o he c ude
eac ion. Un o una ely, NOESY expe imen s on he unc ionalized γ-lac ams did no
p o ide solid e idence ha could lead o he unambiguous de e mina ion o he ela i e
con igu a ion o he adduc . Fo his eason, a single c ys al o subs a e 12b was isola ed
om a mix u e o CH2Cl2/hexanes and, nex , he s uc u e ob ained by X- ay di ac ion
expe imen s e ealed unequi ocally a ela i e con igu a ion de i ed om he an-
i-addi ion o he γ-lac am co e o he aldehyde elec ophile (Figu e 2). A plausible an-
si ion s a e leading o he an i-de i a i e may consis o an elec os a ic in e ac ion be-
ween he aldehyde and he li hium ca ion, di ec ing he ca bonyl g oup owa ds he
py ole ing. A possible addi ional s abiliza ion by hyd ogen bonding be ween he NH
subs i uen and he ca bonyl oxygen may p o ide a e y igid a angemen o he alde-
hyde, which o ien s i s e minal hyd ogen in a gauche con o ma ion ela i e o he bulky
phospho us subs i uen , as d awn in he Newman p ojec ion shown in Figu e 2.
Figu e 2. Plausible ansi ion s a e o he nucleophilic addi ion o e hyl glyoxala e and X- ay
s uc u e o unc ionalized γ-lac am 12b (H, whi e; C, g ey, O, ed, N, blue, P, pink) (R, R enan i-
ome shown).
Su p isingly, unde he same eac ion condi ions, o he special case o he nucle-
ophilic addi ion o phospho a ed γ-lac am 4d o p-ni ophenyl isocyana e, he in oduc-
ion o an imine moie y in o he i e-membe ed ing was obse ed o gi e γ-lac am 13
(Scheme 5). An explana ion o his beha io may consis o an ini ial o ma ion o he
amide 14 by he ypical nucleophilic addi ion o an isocyana e subs a e. Then, a spon-
aneous oxida ion o he 5-membe ed he e ocycle is p oposed o yield in e media e 15.
Nex , an in amolecula conjuga e addi ion o he amide ni ogen o he he e ocycle
would a o d he ins able h ee-membe ed azi idinone species 16, and a subsequen e-
a angemen o he azi idinone and he enamine moie ies a he γ-lac am co e would lead
o N- o mamide 17 ha unde goes a spon aneous clea age o he o myl esidue o a o d
imine- unc ionalized γ-lac am 13.
Figu e 2.
Plausible ansi ion s a e o he nucleophilic addi ion o e hyl glyoxala e and X- ay s uc u e
o unc ionalized
γ
-lac am
12b
(H, whi e; C, g ey, O, ed, N, blue, P, pink) (R,Renan iome shown).
Su p isingly, unde he same eac ion condi ions, o he special case o he nucleophilic
addi ion o phospho a ed
γ
-lac am
4d
o p-ni ophenyl isocyana e, he in oduc ion o an
imine moie y in o he i e-membe ed ing was obse ed o gi e
γ
-lac am
13
(Scheme 5).
An explana ion o his beha io may consis o an ini ial o ma ion o he amide
14
by he
ypical nucleophilic addi ion o an isocyana e subs a e. Then, a spon aneous oxida ion o
he 5-membe ed he e ocycle is p oposed o yield in e media e
15
. Nex , an in amolecula
conjuga e addi ion o he amide ni ogen o he he e ocycle would a o d he ins able h ee-
membe ed azi idinone species
16
, and a subsequen ea angemen o he azi idinone and
he enamine moie ies a he
γ
-lac am co e would lead o N- o mamide
17
ha unde goes a
spon aneous clea age o he o myl esidue o a o d imine- unc ionalized γ-lac am 13.
Molecules 2022, 27, x FOR PEER REVIEW 7 o 26
N
H
p-Tol
N
O
p-Tol
N
H
p-Tol
N
O
p-Tol
N
4d
PPh
2
O
PPh
2
O
13 (62%)
p-NO
2
C
6
H
4
1. LDA, THF, -78ºC
2. p-NO
2
C
6
H
4
-N=C=O, −78ºC o
N
H
p-Tol
N
O
p-Tol
PPh
2
O
O
H
N
p-NO
2
C
6
H
4
Np-Tol
N
O
p-Tol
PPh
2
O
Np-Tol
N
O
p-Tol
N
PPh
2
O
p-NO
2
C
6
H
4
O
15
17
14
O
H
N
p-NO
2
C
6
H
4
N
H
p-Tol
N
O
p-Tol
PPh
2
O
N
p-NO
2
C
6
H
4
O
16
Scheme 5. Unexpec ed γ-lac am de i a i e 13 ob ained by nucleophilic addi ion o γ-lac am 4d o
isocyana es.
Due o he complexi y o he ans o ma ion p oposed and, in iew o he simple
pa e n ob ained in he
1
H NMR spec um, which only shows a oma ic p o ons and he
acidic NH g oup, we we e s ill skep ical abou he eal iden i y o he subs a e ob ained
in he eac ion. Al hough he exac mass was consis en wi h he p oposed s uc u e, in
o de o wipe away any doub ega ding he iden i y o subs a e 13, a monoc ys al o
γ-lac am de i a i e 13 was isola ed and i s s uc u e was unambiguously es ablished by
X- ay di ac ion (Figu e 3). Key ea u es o he c ys al s uc u e o 13 a e he pa allel
con o ma ion o he N-a yl g oups a he lac am ni ogen and he imine g oup, possibly
s abilized by π-s acking, and he in amolecula hyd ogen bonding obse ed be ween
he enamine NH and he phospho yl oxygen.
Figu e 3. X- ay s uc u e o unc ionalized γ-lac am 13 (H, whi e; C, g ey, O, ed, N, blue, P, pink).
Nex , he unc ionaliza ion eac ion was ex ended o he use o chi al γ-lac am de-
i a i es 5 holding a subs i uen a posi ion 5 o he he e ocycle. Unde simila condi-
ions, he ea men o subs i u ed γ-lac am 5a wi h LDA a low empe a u e, ollowed by
he addi ion o me hyl iodide, a o ded he alkyla ed subs a e 18 in mode a e yield
(51%), oge he wi h a small amoun o he hyd olyzed enol-de i ed lac am 19 (26%)
(Scheme 6). The same beha io has al eady been obse ed in simila highly unc ional-
ized 3-amino 3-py olin-2-ones and was a ibu ed o he high s e ic hind ance a he
5-membe ed ing, due o he high deg ee o subs i u ion [20–25]. In addi ion,
enol-de i ed subs a e 19 can be p epa ed in an almos quan i a i e yield by he hyd ol-
ysis o enamine-de i ed γ-lac am 18 in 0.1 M aqueous hyd ochlo ic acid. Un o una ely,
unde he same eac ion condi ions, he nucleophilic addi ion o γ-lac am 5a o o he
elec ophiles, such as ace ylene ca boxyla es, ac yla es, o bulkie alkyl halides, ailed,
which was a ibu ed o he high s e ic c owding p esen in he expec ed densely unc-
ionalized esul ing subs a es.
Scheme 5.
Unexpec ed
γ
-lac am de i a i e
13
ob ained by nucleophilic addi ion o
γ
-lac am
4d
o isocyana es.
Due o he complexi y o he ans o ma ion p oposed and, in iew o he simple
pa e n ob ained in he
1
H NMR spec um, which only shows a oma ic p o ons and he
acidic NH g oup, we we e s ill skep ical abou he eal iden i y o he subs a e ob ained
in he eac ion. Al hough he exac mass was consis en wi h he p oposed s uc u e, in
Molecules 2022,27, 3624 7 o 25
o de o wipe away any doub ega ding he iden i y o subs a e
13
, a monoc ys al o
γ
-lac am de i a i e
13
was isola ed and i s s uc u e was unambiguously es ablished by
X- ay di ac ion (Figu e 3). Key ea u es o he c ys al s uc u e o
13
a e he pa allel
con o ma ion o he N-a yl g oups a he lac am ni ogen and he imine g oup, possibly
s abilized by
π
-s acking, and he in amolecula hyd ogen bonding obse ed be ween he
enamine NH and he phospho yl oxygen.
Molecules 2022, 27, x FOR PEER REVIEW 7 o 26
N
H
p-Tol
N
O
p-Tol
N
H
p-Tol
N
O
p-Tol
N
4d
PPh
2
O
PPh
2
O
13 (62%)
p-NO
2
C
6
H
4
1. LDA, THF, -78ºC
2. p-NO
2
C
6
H
4
-N=C=O, −78ºC o
N
H
p-Tol
N
O
p-Tol
PPh
2
O
O
H
N
p-NO
2
C
6
H
4
Np-Tol
N
O
p-Tol
PPh
2
O
Np-Tol
N
O
p-Tol
N
PPh
2
O
p-NO
2
C
6
H
4
O
15
17
14
O
H
N
p-NO
2
C
6
H
4
N
H
p-Tol
N
O
p-Tol
PPh
2
O
N
p-NO
2
C
6
H
4
O
16
Scheme 5. Unexpec ed γ-lac am de i a i e 13 ob ained by nucleophilic addi ion o γ-lac am 4d o
isocyana es.
Due o he complexi y o he ans o ma ion p oposed and, in iew o he simple
pa e n ob ained in he
1
H NMR spec um, which only shows a oma ic p o ons and he
acidic NH g oup, we we e s ill skep ical abou he eal iden i y o he subs a e ob ained
in he eac ion. Al hough he exac mass was consis en wi h he p oposed s uc u e, in
o de o wipe away any doub ega ding he iden i y o subs a e 13, a monoc ys al o
γ-lac am de i a i e 13 was isola ed and i s s uc u e was unambiguously es ablished by
X- ay di ac ion (Figu e 3). Key ea u es o he c ys al s uc u e o 13 a e he pa allel
con o ma ion o he N-a yl g oups a he lac am ni ogen and he imine g oup, possibly
s abilized by π-s acking, and he in amolecula hyd ogen bonding obse ed be ween
he enamine NH and he phospho yl oxygen.
Figu e 3. X- ay s uc u e o unc ionalized γ-lac am 13 (H, whi e; C, g ey, O, ed, N, blue, P, pink).
Nex , he unc ionaliza ion eac ion was ex ended o he use o chi al γ-lac am de-
i a i es 5 holding a subs i uen a posi ion 5 o he he e ocycle. Unde simila condi-
ions, he ea men o subs i u ed γ-lac am 5a wi h LDA a low empe a u e, ollowed by
he addi ion o me hyl iodide, a o ded he alkyla ed subs a e 18 in mode a e yield
(51%), oge he wi h a small amoun o he hyd olyzed enol-de i ed lac am 19 (26%)
(Scheme 6). The same beha io has al eady been obse ed in simila highly unc ional-
ized 3-amino 3-py olin-2-ones and was a ibu ed o he high s e ic hind ance a he
5-membe ed ing, due o he high deg ee o subs i u ion [20–25]. In addi ion,
enol-de i ed subs a e 19 can be p epa ed in an almos quan i a i e yield by he hyd ol-
ysis o enamine-de i ed γ-lac am 18 in 0.1 M aqueous hyd ochlo ic acid. Un o una ely,
unde he same eac ion condi ions, he nucleophilic addi ion o γ-lac am 5a o o he
elec ophiles, such as ace ylene ca boxyla es, ac yla es, o bulkie alkyl halides, ailed,
which was a ibu ed o he high s e ic c owding p esen in he expec ed densely unc-
ionalized esul ing subs a es.
Figu e 3. X- ay s uc u e o unc ionalized γ-lac am 13 (H, whi e; C, g ey, O, ed, N, blue, P, pink).
Nex , he unc ionaliza ion eac ion was ex ended o he use o chi al
γ
-lac am de i a-
i es
5
holding a subs i uen a posi ion 5 o he he e ocycle. Unde simila condi ions,
he ea men o subs i u ed
γ
-lac am
5a
wi h LDA a low empe a u e, ollowed by he
addi ion o me hyl iodide, a o ded he alkyla ed subs a e
18
in mode a e yield (51%),
oge he wi h a small amoun o he hyd olyzed enol-de i ed lac am 19 (26%) (Scheme 6).
The same beha io has al eady been obse ed in simila highly unc ionalized 3-amino
3-py olin-2-ones and was a ibu ed o he high s e ic hind ance a he 5-membe ed ing,
due o he high deg ee o subs i u ion [
20
–
25
]. In addi ion, enol-de i ed subs a e
19
can be
p epa ed in an almos quan i a i e yield by he hyd olysis o enamine-de i ed
γ
-lac am
18
in 0.1 M aqueous hyd ochlo ic acid. Un o una ely, unde he same eac ion condi ions, he
nucleophilic addi ion o
γ
-lac am
5a
o o he elec ophiles, such as ace ylene ca boxyla es,
ac yla es, o bulkie alkyl halides, ailed, which was a ibu ed o he high s e ic c owding
p esen in he expec ed densely unc ionalized esul ing subs a es.
Molecules 2022, 27, x FOR PEER REVIEW 8 o 26
Scheme 6. Enamine unc ionaliza ion o 5-subs i u ed γ-lac am 5a.
The alkyla ion a C-5 in γ-lac am de i a i e 18 was e i ied by an ex ensi e NMR
s udy. The selec i e unc ionaliza ion is deduced in he 1H NMR spec um om he dis-
appea ance o he wo double s a δH = 6.01 and 5.63 ppm (3JHH = 2.6 Hz), co esponding o
he wo CH g oups o he γ-lac am ing in s a ing subs a e 5a, and he appea ance o a
new single a δH = 5.33 ppm assigned, in p inciple, o he p o on a he chi al ca bon o
he he e ocycle in 18. The p esence o he me hyl g oup is e iden om he p esence o an
in ense single a δH = 1.60 ppm.
The mos cha ac e is ic signals ound in he 13C NMR spec um o 18 a e he ou
ca bons o he 5-membe ed he e ocycle, comp ising he chi al CH ca bon a δC = 67.6
ppm, he wo qua e na y enamine ca bons a δC = 125.7 and 131.3 ppm, and he conju-
ga ed amide ca bonyl g oup a δC = 168.2 ppm. Likewise, he p esence o a dime hyla-
minome hyl g oup is e idenced om he appea ance o an in ense signal a δC = 13.6
ppm. The mul iplici y o all ca bon signals was e i ied by DEPT expe imen s. In addi-
ion, a s ong C-H in e ac ion was obse ed in HSQC spec um be ween he 1H NMR and
13C NMR signals a ibu ed o he CH, and me hyl g oups.
HMBC expe imen s p o ide addi ional e idence o he unc ionaliza ion a C-4 in
subs a e 18. Acco dingly, a co ela ion is obse ed o bo h, he CH and me hyl p o ons,
wi h he wo qua e na y ca bons o he enamine moie y. Mo eo e , he 1H NMR signal
assigned o he me hyl g oup shows a co espondence wi h he s e eogenic ca bon a he
5-membe ed he e ocycle, while he me hine p o on p esen s he ecip ocal co ela ion.
On he o he hand, he p esence o an es e g oup a he s e eogenic ca bon o he
γ-lac am ing p o ides an addi ional acidic cha ac e o he p o on a C-5. Acco dingly,
he inylogous Mannich eac ion o 3-py olin-2-one 5g is obse ed upon ea men wi h
ime hylamine in he p esence o Eschenmose sal , p o iding, in good yield, γ-lac am
20, bea ing a e asubs i u ed ca bon (Scheme 7).
Scheme 7. Vinylogous eac ion o γ-lac am 5b wi h Eschenmose sal .
In o de o p o ide e idence o he selec i e unc ionaliza ion a C-5, an ex ensi e
NMR s udy o subs a e 20 was implemen ed. In his case, he 1H NMR spec um o
subs a e 20 shows a single a δH = 5.95 ppm o he me hine g oup and wo addi ional
double s a δH = 2.74 and 3.17 ppm, cha ac e is ic o he wo dias e eo opic p o ons o he
me hylene g oup, showing a ypical geminal coupling cons an (2JHH = 14.0 Hz). As ex-
pec ed, he double s co esponding o he dias e eo opic p o ons show a s ong in e ac-
ion in he COSY spec um.
The mos cha ac e is ic signals ound in he 13C NMR spec um a e he ou ca bons
o he 5-membe ed he e ocycle, comp ising he chi al qua e na y ca bon a δC = 72.7 ppm,
he wo enamine ca bons a δC = 105 and 134 ppm, and he amide ca bonyl g oup a δC =
168.3 ppm. The unc ionaliza ion a C-5 in 20 is deduced om he appea ance o he
qua e na y ca bon a highe ield han in C-4- unc ionalized subs a e 18 (72.7 s. 125.7
Scheme 6. Enamine unc ionaliza ion o 5-subs i u ed γ-lac am 5a.
The alkyla ion a C-5 in
γ
-lac am de i a i e
18
was e i ied by an ex ensi e NMR s udy.
The selec i e unc ionaliza ion is deduced in he
1
H NMR spec um om he disappea ance
o he wo double s a
δH
= 6.01 and 5.63 ppm (
3
J
HH
= 2.6 Hz), co esponding o he wo CH
g oups o he
γ
-lac am ing in s a ing subs a e
5a
, and he appea ance o a new single a
δH
= 5.33 ppm assigned, in p inciple, o he p o on a he chi al ca bon o he he e ocycle in
18
. The p esence o he me hyl g oup is e iden om he p esence o an in ense single a
δH= 1.60 ppm.
The mos cha ac e is ic signals ound in he
13
C NMR spec um o
18
a e he ou
ca bons o he 5-membe ed he e ocycle, comp ising he chi al CH ca bon a
δC
= 67.6 ppm,
he wo qua e na y enamine ca bons a
δC
= 125.7 and 131.3 ppm, and he conjuga ed amide
ca bonyl g oup a
δC
= 168.2 ppm. Likewise, he p esence o a dime hylaminome hyl g oup
Molecules 2022,27, 3624 8 o 25
is e idenced om he appea ance o an in ense signal a
δC
= 13.6 ppm. The mul iplici y o
all ca bon signals was e i ied by DEPT expe imen s. In addi ion, a s ong C-H in e ac ion
was obse ed in HSQC spec um be ween he
1
H NMR and
13
C NMR signals a ibu ed o
he CH, and me hyl g oups.
HMBC expe imen s p o ide addi ional e idence o he unc ionaliza ion a C-4 in
subs a e
18
. Acco dingly, a co ela ion is obse ed o bo h, he CH and me hyl p o ons,
wi h he wo qua e na y ca bons o he enamine moie y. Mo eo e , he
1
H NMR signal
assigned o he me hyl g oup shows a co espondence wi h he s e eogenic ca bon a he
5-membe ed he e ocycle, while he me hine p o on p esen s he ecip ocal co ela ion.
On he o he hand, he p esence o an es e g oup a he s e eogenic ca bon o he
γ
-lac am ing p o ides an addi ional acidic cha ac e o he p o on a C-5. Acco dingly,
he inylogous Mannich eac ion o 3-py olin-2-one
5g
is obse ed upon ea men wi h
ime hylamine in he p esence o Eschenmose sal , p o iding, in good yield,
γ
-lac am
20
,
bea ing a e asubs i u ed ca bon (Scheme 7).
Molecules 2022, 27, x FOR PEER REVIEW 8 o 26
Scheme 6. Enamine unc ionaliza ion o 5-subs i u ed γ-lac am 5a.
The alkyla ion a C-5 in γ-lac am de i a i e 18 was e i ied by an ex ensi e NMR
s udy. The selec i e unc ionaliza ion is deduced in he 1H NMR spec um om he dis-
appea ance o he wo double s a δH = 6.01 and 5.63 ppm (3JHH = 2.6 Hz), co esponding o
he wo CH g oups o he γ-lac am ing in s a ing subs a e 5a, and he appea ance o a
new single a δH = 5.33 ppm assigned, in p inciple, o he p o on a he chi al ca bon o
he he e ocycle in 18. The p esence o he me hyl g oup is e iden om he p esence o an
in ense single a δH = 1.60 ppm.
The mos cha ac e is ic signals ound in he 13C NMR spec um o 18 a e he ou
ca bons o he 5-membe ed he e ocycle, comp ising he chi al CH ca bon a δC = 67.6
ppm, he wo qua e na y enamine ca bons a δC = 125.7 and 131.3 ppm, and he conju-
ga ed amide ca bonyl g oup a δC = 168.2 ppm. Likewise, he p esence o a dime hyla-
minome hyl g oup is e idenced om he appea ance o an in ense signal a δC = 13.6
ppm. The mul iplici y o all ca bon signals was e i ied by DEPT expe imen s. In addi-
ion, a s ong C-H in e ac ion was obse ed in HSQC spec um be ween he 1H NMR and
13C NMR signals a ibu ed o he CH, and me hyl g oups.
HMBC expe imen s p o ide addi ional e idence o he unc ionaliza ion a C-4 in
subs a e 18. Acco dingly, a co ela ion is obse ed o bo h, he CH and me hyl p o ons,
wi h he wo qua e na y ca bons o he enamine moie y. Mo eo e , he 1H NMR signal
assigned o he me hyl g oup shows a co espondence wi h he s e eogenic ca bon a he
5-membe ed he e ocycle, while he me hine p o on p esen s he ecip ocal co ela ion.
On he o he hand, he p esence o an es e g oup a he s e eogenic ca bon o he
γ-lac am ing p o ides an addi ional acidic cha ac e o he p o on a C-5. Acco dingly,
he inylogous Mannich eac ion o 3-py olin-2-one 5g is obse ed upon ea men wi h
ime hylamine in he p esence o Eschenmose sal , p o iding, in good yield, γ-lac am
20, bea ing a e asubs i u ed ca bon (Scheme 7).
Scheme 7. Vinylogous eac ion o γ-lac am 5b wi h Eschenmose sal .
In o de o p o ide e idence o he selec i e unc ionaliza ion a C-5, an ex ensi e
NMR s udy o subs a e 20 was implemen ed. In his case, he 1H NMR spec um o
subs a e 20 shows a single a δH = 5.95 ppm o he me hine g oup and wo addi ional
double s a δH = 2.74 and 3.17 ppm, cha ac e is ic o he wo dias e eo opic p o ons o he
me hylene g oup, showing a ypical geminal coupling cons an (2JHH = 14.0 Hz). As ex-
pec ed, he double s co esponding o he dias e eo opic p o ons show a s ong in e ac-
ion in he COSY spec um.
The mos cha ac e is ic signals ound in he 13C NMR spec um a e he ou ca bons
o he 5-membe ed he e ocycle, comp ising he chi al qua e na y ca bon a δC = 72.7 ppm,
he wo enamine ca bons a δC = 105 and 134 ppm, and he amide ca bonyl g oup a δC =
168.3 ppm. The unc ionaliza ion a C-5 in 20 is deduced om he appea ance o he
qua e na y ca bon a highe ield han in C-4- unc ionalized subs a e 18 (72.7 s. 125.7
Scheme 7. Vinylogous eac ion o γ-lac am 5b wi h Eschenmose sal .
In o de o p o ide e idence o he selec i e unc ionaliza ion a C-5, an ex ensi e NMR
s udy o subs a e
20
was implemen ed. In his case, he
1
H NMR spec um o subs a e
20
shows a single a
δH
= 5.95 ppm o he me hine g oup and wo addi ional double s a
δH
= 2.74 and 3.17 ppm, cha ac e is ic o he wo dias e eo opic p o ons o he me hylene
g oup, showing a ypical geminal coupling cons an (
2
J
HH
= 14.0 Hz). As expec ed, he
double s co esponding o he dias e eo opic p o ons show a s ong in e ac ion in he
COSY spec um.
The mos cha ac e is ic signals ound in he
13
C NMR spec um a e he ou ca bons
o he 5-membe ed he e ocycle, comp ising he chi al qua e na y ca bon a
δC
= 72.7 ppm,
he wo enamine ca bons a
δC
= 105 and 134 ppm, and he amide ca bonyl g oup a
δC
= 168.3 ppm. The unc ionaliza ion a C-5 in
20
is deduced om he appea ance o
he qua e na y ca bon a highe ield han in C-4- unc ionalized subs a e
18
(72.7 s.
125.7 ppm), sugges ing a sp
3
hyb idiza ion o such ca bon. Mo eo e , he ac ha he CH
ca bon appea s a signi ican ly lowe ield in he
13
C NMR spec um o
20
han in subs a e
17
(104.9 s. 67.6 ppm) sugges s ha his signal co esponds o an ole inic me hine ca bon.
As usual, he mul iplici y o he ca bons was e i ied by DEPT expe imen s and could also
be deduced om he in e ac ions obse ed in he HSQC spec um.
Some addi ional e idences o he unc ionaliza ion a C-5 in subs a e
20
can be
ga he ed om HMBC expe imen s. In his case, he p incipal a gumen o conside a C-5
unc ionaliza ion a ises om he s ong co ela ion obse ed be ween he dias e eo opic
me hylene p o ons and he ca boxylic ca bon, co esponding o he es e moie y. Mo eo e ,
bo h dias e eo opic p o ons show an addi ional in e ac ion wi h he enamine CH g oup,
while no co espondence wi h he qua e na y enamine ca bon is obse ed.
Conside ing he p esence o a chi al s e eocen e in C-5-subs i u ed
γ
-lac am sub-
s a es
5
, nex , some o he dias e eoselec i e ans o ma ions we e explo ed. A simple
ans o ma ion o subs a e
5b
consis s o he hyd ogena ion o he endocyclic enamine
moie y unde hyd ogen p essu e (80 psi) in he p esence o palladium as ca alys , leading
o he o ma ion o a single dias e eoisome o sa u a ed
γ
-lac am de i a i e
21
in excellen
yield (Scheme 8).
Molecules 2022,27, 3624 9 o 25
Molecules 2022, 27, x FOR PEER REVIEW 9 o 26
ppm), sugges ing a sp3 hyb idiza ion o such ca bon. Mo eo e , he ac ha he CH
ca bon appea s a signi ican ly lowe ield in he 13C NMR spec um o 20 han in sub-
s a e 17 (104.9 s. 67.6 ppm) sugges s ha his signal co esponds o an ole inic me hine
ca bon. As usual, he mul iplici y o he ca bons was e i ied by DEPT expe imen s and
could also be deduced om he in e ac ions obse ed in he HSQC spec um.
Some addi ional e idences o he unc ionaliza ion a C-5 in subs a e 20 can be
ga he ed om HMBC expe imen s. In his case, he p incipal a gumen o conside a C-5
unc ionaliza ion a ises om he s ong co ela ion obse ed be ween he dias e eo opic
me hylene p o ons and he ca boxylic ca bon, co esponding o he es e moie y. Mo e-
o e , bo h dias e eo opic p o ons show an addi ional in e ac ion wi h he enamine CH
g oup, while no co espondence wi h he qua e na y enamine ca bon is obse ed.
Conside ing he p esence o a chi al s e eocen e in C-5-subs i u ed γ-lac am sub-
s a es 5, nex , some o he dias e eoselec i e ans o ma ions we e explo ed. A simple
ans o ma ion o subs a e 5b consis s o he hyd ogena ion o he endocyclic enamine
moie y unde hyd ogen p essu e (80 psi) in he p esence o palladium as ca alys , leading
o he o ma ion o a single dias e eoisome o sa u a ed γ-lac am de i a i e 21 in excel-
len yield (Scheme 8).
Scheme 8. Dias e eoselec i e eac ions o γ-lac am 5g.
The ela i e con igu a ion o he s e eocen e s in sa u a ed γ-lac am 21 was de e -
mined by NOESY (see ESI). The ac ha he signals co esponding o bo h p o ons a he
wo s e eogenic cen e s, a δ = 4.78 and 4.16 ppm, show a s ong NOE e ec wi h he same
p o on a he dias e eo opic me hylene g oup a δ = 3.10 ppm, sugges s ha hese h ee
a oms a e o ien ed in he same di ec ion. In addi ion, no signi ican NOE is obse ed
be ween he signal co esponding o he second o he dias e eo opic p o ons, a δ = 2.08
ppm, and he wo p o ons a bo h s e eogenic cen e s, which con i ms a ela i e cis con-
igu a ion be ween he ca boxyla e and he amino g oups in s uc u e 21. Thus, he con-
en ional mechanism o a ca aly ic hyd ogena ion o a ca bon-ca bon double bond is
deduced om his con igu a ion, whe e a syn addi ion o hyd ogen akes place om he
less hinde ed ace, ha is, he opposi e o he ca boxyla e subs i uen a he s e eogenic
ca bon.
In addi ion, simila cyclic enamines ha e p o ed o be excellen subs a es in [3+3]
annula ion eac ions [12]. Fo his eason, enamine-de i ed chi al lac am 5b was ea ed
wi h β,γ-unsa u a ed α-ke oes e 22 in he p esence o a ca aly ic amoun o y e bium
i la e, leading o he o ma ion o a single dias e eoisome o bicyclic dihyd opy idine
23 in excellen yield (Scheme 8). In his case, NOESY expe imen s showed a s ong co -
ela ion be ween bo h p o ons a he chi al cen e s a δ = 4.93 and 5.05 ppm, e ealing a cis
ela i e con igu a ion o bo h subs i uen s a he s e eogenic ca bons (see ESI). In his
Scheme 8. Dias e eoselec i e eac ions o γ-lac am 5g.
The ela i e con igu a ion o he s e eocen e s in sa u a ed
γ
-lac am
21
was de e mined
by NOESY (see ESI). The ac ha he signals co esponding o bo h p o ons a he wo
s e eogenic cen e s, a
δ
= 4.78 and 4.16 ppm, show a s ong NOE e ec wi h he same p o on
a he dias e eo opic me hylene g oup a
δ
= 3.10 ppm, sugges s ha hese h ee a oms
a e o ien ed in he same di ec ion. In addi ion, no signi ican NOE is obse ed be ween
he signal co esponding o he second o he dias e eo opic p o ons, a δ= 2.08 ppm, and
he wo p o ons a bo h s e eogenic cen e s, which con i ms a ela i e cis con igu a ion
be ween he ca boxyla e and he amino g oups in s uc u e
21
. Thus, he con en ional
mechanism o a ca aly ic hyd ogena ion o a ca bon-ca bon double bond is deduced om
his con igu a ion, whe e a syn addi ion o hyd ogen akes place om he less hinde ed
ace, ha is, he opposi e o he ca boxyla e subs i uen a he s e eogenic ca bon.
In addi ion, simila cyclic enamines ha e p o ed o be excellen subs a es in [3+3]
annula ion eac ions [
12
]. Fo his eason, enamine-de i ed chi al lac am
5b
was ea ed
wi h
β
,
γ
-unsa u a ed
α
-ke oes e
22
in he p esence o a ca aly ic amoun o y e bium
i la e, leading o he o ma ion o a single dias e eoisome o bicyclic dihyd opy idine
23
in excellen yield (Scheme 8). In his case, NOESY expe imen s showed a s ong co ela ion
be ween bo h p o ons a he chi al cen e s a
δ
= 4.93 and 5.05 ppm, e ealing a cis ela i e
con igu a ion o bo h subs i uen s a he s e eogenic ca bons (see ESI). In his case, in
ag eemen wi h he p oposed pa hway o his eac ion [
49
], he mechanism o he p ocess
may consis o a Michael addi ion o he enamine moie y o he conjuga ed double bond o
β
,
γ
-unsa u a ed
α
-ke oes e and a second nucleophilic addi ion o he enamine ni ogen o
he ca bonyl g oup. A non-co alen a ac i e in e ac ion o he ca bonyl moie y wi h he
elec on-de icien a ene bea ing he ni o-elec on-wi hd awing subs i uen [
50
] may d i e
he s e eoselec i i y o he eac ion o he exclusi e o ma ion o he cis dias e eoisome as
shown in Figu e 4.
Molecules 2022, 27, x FOR PEER REVIEW 10 o 26
case, in ag eemen wi h he p oposed pa hway o his eac ion [49], he mechanism o
he p ocess may consis o a Michael addi ion o he enamine moie y o he conjuga ed
double bond o β,γ-unsa u a ed α-ke oes e and a second nucleophilic addi ion o he
enamine ni ogen o he ca bonyl g oup. A non-co alen a ac i e in e ac ion o he
ca bonyl moie y wi h he elec on-de icien a ene bea ing he ni o-elec on-wi hd awing
subs i uen [50] may d i e he s e eoselec i i y o he eac ion o he exclusi e o ma ion
o he cis dias e eoisome as shown in Figu e 4.
Figu e 4. P oposed model o he double nucleophilic addi ion o cyclic enamine 5b o
β,γ-unsa u a ed α-ke oes e 22 (S enan iome shown).
Nex , aking he ad an age o he possible in si u au ome iza ion o he enamine
in o an imine moie y, he po en ial o unsa u a ed γ-lac am subs a es as elec ophiles
was s udied. Acco dingly, he ea men o 5-subs i u ed γ-lac am 5a de i ed om
p- oluidine (R1 = p-MeC6H4) wi h me hylli hium in THF a low empe a u e led o he e -
icien o ma ion o unsa u a ed lac am de i a i e 25a, holding a e asubs i u ed chi al
ca bon (Scheme 9). Nex , he eac ion was ex ended o he use o n-bu ylli hium, ob ain-
ing almos iden ical esul s unde he same eac ion condi ions (Scheme 9, 25b). The
scope o he eac ion using n-bu ylli hium as nucleophilic eagen was also ex ended o
he use o o he γ-lac am subs a es 5c–e, de i ed om di e en a oma ic amines such as
p-anisidine, p-b omoaniline and m-chlo oaniline (R1 = p-MeOC6H4, p-B C6H4, m-ClC6H4),
p o iding e asubs i u ed γ-lac am de i a i es 25c–e also in e y good yields (Scheme
9).
Scheme 9. Nucleophilic addi ion o o ganoli hium eagen s o γ-lac ams 5.
The o ma ion o subs a es 25 was e iden by he p esence o a chemical shi in he
1H NMR spec um o compound 25a (R1 = p-Me-C6H4, R2 = Me) a δ = 5.63 ppm, co e-
sponding o he ole inic p o on a he 5-membe ed ing, oge he wi h he wo cha ac e -
Figu e 4.
P oposed model o he double nucleophilic addi ion o cyclic enamine
5b
o
β
,
γ
-
unsa u a ed α-ke oes e 22 (S enan iome shown).
Molecules 2022,27, 3624 16 o 25
1677 (C=O
s
), 1608 (C=C
s
) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o C
22
H
17
F
6
N
2
O
2
455.1194, Found 455.1187.
P ocedu e o he Ca aly ic Hyd ogena ion o 7a
A solu ion o (E)-3-(5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ol-3-yl) ac y-
la e (
7a
) (363 mg, 1mmol) in MeOH (5 mL) was s i ed o 2 days unde H
2
p essu e (80 psi)
in he p esence o palladium on ca bon (10%) (213 mg, 10% mmol). The eac ion mix u e
was il e ed h ough celi e and concen a ed unde acuum. The c ude esidue was pu i ied
by c ys alliza ion (Dichlo ome hane/Hexanes 1:3), a o ding pu e sa u a ed γ-lac am 7.
Me hyl 3-((3R*,4R*)-5-oxo-1-(p- olyl)-4-(p- olylamino)py olidin-3-yl)p opanoa e (
8
). The
p ocedu e was ollowed, a o ding 327 mg (90%) o
8
as whi e c ys als M.p.
(Dichlo ome hane/Hexanes) = 158–160
◦
C.
1
H NMR (400 MHz, CDCl
3
)
δ
7.54 (d,
3JHH = 8.5 Hz
,
2H, 2
×
CH
A
), 7.21 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 7.04 (d,
3
J
HH
= 8.4 Hz, 2H,
2×CHA
), 6.63 (d,
3
J
HH
= 8.4 Hz, 2H,
2×CHA
), 4.47 (s, 1H, NH), 4.13 (dd,
3JHH = 7.2 Hz
,
4JHH = 2.0 Hz
, 1H, NCH), 4.00 (dd,
2
J
HH
= 10.2 Hz,
3
J
HH
= 5.8 Hz, 1H, NC
HA
H
B
), 3.59 (s,
3H, OCH
3
), 2.91 (m, 1H, CH), 2.43–2.29 (m, 5H, CH
3
Tol + COCH
2
), 2.27 (s, 3H, CH
3
Tol), 1.96
(m, 1H, CH), 1.54 (m, 1H, CH
AHB
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
173.5 (C=O),
171.4 (C=O), 145.4 (C
qua
), 136.7 (C
qua
), 134.9 (C
qua
), 130.0 (2
×
CH
A
), 129.7 (
2×CHA
),
127.8 (C
qua
), 119.8 (2
×
CH
A
), 113.5 (2
×
CH
A
), 60.0 (CH), 51.7 (OCH
3
), 50.1 (CH
2
),
37.1 (CH), 31.7 (CH
2
), 23.0 (CH
2
), 21.0 (CH
3
Tol), 20.5 (CH
3
Tol) ppm. FTIR (nea )
νmax
:
3325 (
NH s
), 1733 (C=O
s
), 1698 (C=O
s
) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o
C22H27N2O3367.2022, Found 367.2011.
P ocedu e o he In amolecula Cycliza ion o 8
To a suspension o NaH (29 mg, 1.2 mmol) in oluene (3 mL) was added nea 3-
((3R*,4R*)-5-oxo-1-(p- olyl)-4-(p- olylamino)py olidin-3-yl)p opanoa e (
8
) (366 mg, 1mmol).
The eac ion was s i ed unde e lux o e nigh and he esul ing mix u e was hen
quenched wi h wa e (10 mL) and ex ac ed wi h dichlo ome hane (2
×
10 mL). The
combined o ganic laye s we e d ied o e MgSO
4
and concen a ed unde acuum and
he c ude esidue was pu i ied by ch oma og aphy (Hexanes/AcOE 1:1), a o ding pu e
bicyclic γ-lac am 9.
(4aR*,7aR*)-1,6-Di-p- olylhexahyd o-1H-py olo[3,4-b]py idine-2,7-dione (
9
). The p o-
cedu e was ollowed, a o ding 330 mg (98%) o
9
as a pale yellow oil.
1
H NMR (400 MHz,
CDCl
3
)
δ
7.51 (d,
3
J
HH
= 8.6 Hz, 2H, 2
×
CH
A
), 7.37 (d,
3
J
HH
= 8.4 Hz, 2H, 2
×
CH
A
),
7.19 (d,
3
J
HH
= 8.4 Hz, 2H, 2
×
CH
A
), 7.17 (d,
3
J
HH
= 8.6 Hz, 2H, 2
×
CH
A
), 4.65 (d,
3JHH = 8.0 Hz
, 1H, NCH), 4.04 (dd,
2
J
HH
= 10.1 Hz,
3
J
HH
= 6.4 Hz, 1H, NC
HA
CH
B
), 3.56 (d,
2
J
HH
= 10.1 Hz, 1H, NCH
A
C
HB
), 3.00 (p,
3
J
HH
= 7.0 Hz, 1H, CH), 2.54 ( ,
3
J
HH
= 6.7 Hz, 2H,
COCH
2
), 2.34 (s, 3H, CH
3
Tol), 2.33 (s, 3H, CH
3
Tol), 2.16–1.92 (m, 2H, COCH
2
C
H2
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
170.4 (C=O), 169.7 (C=O), 139.7 (C
qua
), 136.9 (C
qua
),
136.4 (C
qua
), 134.9 (C
qua
), 129.6 (2
×
CH
A
), 129.5 (2
×
CH
A
), 127.3 (2
×
CH
A
), 119.5
(2
×
CH
A
), 64.3 (CH), 51.7 (CH
2
), 31.5 (CH
2
), 30.3 (CH), 25.7 (CH
2
), 21.2 (CH
3
Tol), 20.9
(CH
3
Tol) ppm. FTIR (nea )
νmax
: 1698 (C=O
s
), 1673 (C=O
s
) cm
−1
. HRMS (ESI-TOF) m/z:
[M+H]+calcd o C21H23N2O2335.1760, Found 335.1757.
P ocedu e o he Acidic Hyd olysis o 7a
A solu ion o (E)-3-(5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ol-3-yl) ac y-
la e (
7a
) (0.363, 1 mmol) in oluene (2 mL) and 37% aqueous HCl (2 mL) was s i ed a
oom empe a u e o e nigh . The mix u e was dilu ed wi h wa e and ex ac ed wi h
dichlo ome hane (2
×
10 mL). The combined o ganic laye s we e washed wi h wa e
(
2×10 mL
), d ied o e MgSO
4
, and concen a ed unde acuum. The c ude esidue was
pu i ied by ch oma og aphy (Hexanes/AcOE 4:1), a o ding pu e enol-de i ed
γ
-lac am
10 a e c ys alliza ion (E 2O /Pen ane 1:3).
Me hyl (E)-3-(4-hyd oxy-5-oxo-1-(p- olyl)-2,5-dihyd o-1H-py ol-3-yl)ac yla e (
10
).
The p ocedu e was ollowed, a o ding 262 mg (96%) o
9
as whi e c ys als. M.p. (E
2
O

Molecules 2022,27, 3624 17 o 25
/Pen ane) = 239–241
◦
C.
1
H NMR (400 MHz, DMSO-d6)
δ
11.33 (s, 1H, OH), 7.72 (d,
3JHH = 8.7 Hz
, 2H, 2
×
CH
A
), 7.66 (d,
3
J
HH
= 15.9 Hz, 1H, CH=), 7.22 (d,
3
J
HH
= 8.7 Hz, 2H,
2
×
CH
A
), 6.11 (d,
3
J
HH
= 15.9 Hz, 1H, CH=), 4.49 (s, 2H, CH
2
), 3.71 (s, 3H, OCH
3
), 2.29 (s,
3H, CH
3
Tol) ppm.
13
C NMR {
1
H} (101 MHz, DMSO-d6)
δ
167.1 (C=O), 164.6 (C=O), 149.6
(C
qua
), 137.2 (C
qua
), 133.9 (CH=), 133.8 (C
qua
), 129.8 (2
×
CH
A
), 118.8 (2
×
CH
A
), 116.9
(CH=), 114.9 (C
qua
), 52.0 (OCH
3
), 47.2 (CH
2
), 20.9 (CH
3
Tol) ppm. FTIR (nea )
νmax
: 3460
(OH
s
), 3046 (=CH
s
), 1701 (C=O
s
), 1679 (C=O
s
), 1612 (C=C
s
) cm
−1
. HRMS (ESI-TOF)
m/z: [M+H]+calcd o C15H16NO4274.1079, Found 274.1076.
Gene al P ocedu e o he Nucleophilic Addi ion o γ-Lac ams 4c–d o E hyl Glyoxala e
A solu ion o die hyl (5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ol-3-yl)
phosphona e
4c
(414 mg, 1 mmol) in THF (1 mL) was added o a eshly p epa ed solu ion
o LDA (1.2 Eq) in THF (2 mL) a
−
78
◦
C. A e 1 h, a 1.6 M solu ion o e hyl glyoxala e in
oluene (1.2 mmol, 750
µ
L) was added and he eac ion was le o wa m o o e nigh . The
eac ion was quenched wi h a 0.5 M aqueous solu ion o HCl and he esul ing mix u e was
ex ac ed wi h dichlo ome hane (2
×
10 mL). The combined o ganic laye s we e washed
wi h wa e (2
×
10 mL), d ied o e MgSO
4
, and concen a ed unde acuum. The c ude
esidue was pu i ied by ch oma og aphy (Hexanes/AcOE 6:4), a o ding pu e
γ
-lac am
de i a i es 12.
E hyl (R*)-2-((R*)-3-(die hoxyphospho yl)-5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-
1H-py ol-2-yl)-2-hyd oxyace a e (
12a
). The gene al p ocedu e was ollowed using die hyl
(5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ol-3-yl)phosphona e
4c
(414 mg,
1 mmol) a o ding 315 mg (61%) o
12a
as a pale yellow oil.
1
H NMR (400 MHz, CDCl
3
)
δ
7.45
(s, 1H, NH), 7.34 (d,
3
J
HH
= 7.3 Hz, 2H,
2×CHA
), 7.20 (d,
3JHH = 8.0 Hz
, 2H,
2×CHA
),
7.14–7.03 (m, 4H, 4
×
CH
A
), 5.16 ( ,
3
J
HH
= 1.5 Hz, 1H, CH), 4.47 (d,
3JPH = 7.9 Hz
, 1H,
CH), 4.42 (b oad s, 1H, OH), 4.03 (q,
3
J
HH
= 7.2 Hz, 4H, 2
×
CH
2
), 3.94 (q,
3
J
HH
= 7.2 Hz,
2H, CH
2
), 2.35 (s, 3H, CH
3
Tol), 2.32 (s, 3H, CH
3
Tol), 1.47–0.98 (m, 9H, 3
×
CH
3
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
171.5 (C=O), 164.1 (d,
2
J
CP
= 19.4 Hz, C
qua
), 146.2 (d,
3JCP = 7.2 Hz
, C=O), 137.0 (C
qua
), 136.5 (C
qua
), 135.0 (C
qua
), 133.1 (C
qua
), 129.8 (2
×
CH
A
),
129.3 (
2×CHA
), 124.4 (2
×
CH
A
), 123.8 (2
×
CH
A
), 96.4 (d,
1
J
CP
= 211.3 Hz, C
qua
), 70.2
(CH), 63.9 (d,
2
J
CP
= 17.4 Hz, CH), 62.5 (d,
2
J
CP
= 5.5 Hz, CH
2
), 62.4 (d,
2JCP = 5.4 Hz
, CH
2
),
61.8 (CH
2
), 21.2 (CH
3
Tol), 21.1 (CH
3
Tol), 16.3 (d,
3
J
CP
= 6.7 Hz, CH
3
), 16.3 (d,
3JCP = 6.9 Hz
,
CH
3
), 14.1 (CH
3
) ppm.
31
P NMR (162 MHz, CDCl
3
)
δ
19.1 ppm. FTIR (nea )
νmax
: 3430
(OH), 3338 (NH), 1714 (C=O
s
), 1694 (C=O
s
), 1609 (C=C), 1213 (P=O) cm
−1
. HRMS
(ESI-TOF) m/z: [M+H]+calcd o C26H34N2O7P 517.2104, Found 517.2100.
E hyl (R*)-2-((R*)-3-(diphenylphospho yl)-5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-
1H-py ol-2-yl)-2-hyd oxyace a e (
12b
). The gene al p ocedu e was ollowed using 4-
(diphenylphospho yl)-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-2H-py ol-2-one
4d
(478 mg,
1 mmol), a o ding 498 mg (86%) o
12b
as yellow c ys als. M.p. (Dichlo ome hane/Hexanes)
= 211–213
◦
C.
1
H NMR (400 MHz, CDCl
3
)
δ
7.87–7.70 (m, 2H, 2
×
CH
A
), 7.61–7.43 (m, 5H,
5
×
CH
A
), 7.33 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 7.31–7.23 (m, 3H, 3
×
CH
A
), 7.17 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 6.82 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 6.72 (d,
3JHH = 8.2 Hz
,
2H, 2
×
CH
A
), 6.64 (s, 1H, NH), 5.28 (b oad s, 1H, OH), 5.09 ( ,
3
J
HH
= 2.8 Hz, 1H, CH),
4.38 (dd,
3
J
PH
= 9.3 Hz,
3
J
HH
= 2.8 Hz, 1H, CH), 3.91 (q,
3
J
HH
= 7.1 Hz, 2H, CH
2
), 2.33 (s,
3H, CH
3
Tol), 2.21 (s, 3H, CH
3
Tol), 1.12 ( ,
3
J
HH
= 7.1 Hz, 3H, CH
3
) ppm.
13
C NMR {
1
H}
(101 MHz, CDCl
3
)
δ
171.0 (C=O), 164.5 (d,
3
J
CP
= 14.5 Hz, C=O), 144.9 (d,
2JCP = 3.9 Hz
,
C
qua
), 137.2 (C
qua
), 136.7 (d,
4
J
CP
= 1.2 Hz, C
qua
), 133.8 (C
qua
), 133.3 (C
qua
), 132.9 (d,
1JCP = 109.0 Hz
, C
qua
), 132.1 (d,
4
J
CP
= 2.5 Hz, CH
A
), 131.9 (d,
4
J
CP
= 2.9 Hz, CH
A
), 131.3
(d,
2
J
CP
= 9.6 Hz, 2
×
CH
A
), 131.2 (d,
2
J
CP
= 10.3 Hz, 2
×
CH
A
), 131.0 (C
qua
), 129.7
(
2×CHA
), 129.5 (2
×
CH
A
), 129.0 (d,
3
J
CP
= 12.4 Hz, 2
×
CH
A
), 128.6 (d,
3
J
CP
= 12.7 Hz,
2
×
CH
A
), 123.7 (2
×
CH
A
), 121.5 (2
×
CH
A
), 102.5 (d,
1
J
CP
= 113.1 Hz, C
qua
), 70.6 (CH),
64.7 (d,
2
J
CP
= 12.7 Hz, CH), 61.6 (CH
2
), 21.2 (CH
3
Tol), 20.9 (CH
3
Tol), 14.0 (CH
3
) ppm.
31
P
NMR (121 MHz, CDCl
3
)
δ
19.4 ppm. FTIR (nea )
νmax
: 3417 (OH), 3262 (NH), 1720 (C=O),
Molecules 2022,27, 3624 18 o 25
1679 (C=O), 1606 (C=C), 1175 (P=O). HRMS (ESI-TOF) m/z: [M+H]
+
calcd o C
34
H
34
N
2
O
5
P
581.2205, Found 581.2202.
P ocedu e o he Syn hesis o γ-Lac am De i a i e 13
A solu ion o 4-(diphenylphospho yl)-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-2H-
py ol-2-one (
4d
) (478 mg, 1 mmol) in THF (1 mL) was added o a eshly p epa ed
solu ion o LDA (1.2 Eq) in THF (2 mL) a
−
78
◦
C. A e 1 h, a solu ion o 1-isocyana o-4-
ni obenzene (197 mg, 1.2 mmol) in THF (1 mL) was added and he eac ion was le o
wa m o o e nigh . The eac ion was quenched wi h a 0.5 M aqueous solu ion o HCl
and he esul ing mix u e was ex ac ed wi h dichlo ome hane (2
×
10 mL). The combined
o ganic laye s we e washed wi h wa e (2
×
10 mL), d ied o e MgSO
4
, and concen a ed
unde acuum. The c ude esidue was pu i ied by ch oma og aphy (Hexanes/AcOE 4:1),
a o ding pu e γ-lac am de i a i e 13.
4-(Diphenylphospho yl)-5-((4-ni ophenyl)imino)-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-
2H-py ol-2-one (
13
). The p ocedu e was ollowed, a o ding 380 mg (62%) o
13
as an
o ange oil.
1
H NMR (400 MHz, CDCl
3
)
δ
10.54 (s, 1H, NH), 8.03–7.91 (m, 4H, 4
×
CH
A
),
7.66 (d,
3
J
HH
= 8.9 Hz, 2H, 2
×
CH
A
), 7.63–7.56 (m, 2H, 2
×
CH
A
), 7.54–7.47 (m, 4H,
4×CHA
), 7.18 (d,
3
J
HH
= 8.3 Hz, 2H, 2
×
CH
A
), 7.11 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
),
6.76 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 6.66 (d,
3
J
HH
= 8.3 Hz, 2H, 2
×
CH
A
), 6.27 (d,
3JHH = 8.9 Hz
, 2H, 2
×
CH
A
), 2.32 (s, 3H, CH
3
Tol), 2.10 (s, 3H, CH
3
Tol) ppm.
13
C NMR
{
1
H} (101 MHz, CDCl
3
)
δ
164.7 (d,
2
J
CP
= 14.4 Hz, C=N), 153.2 (C
qua
), 152.1 (d,
3JCP = 3.7 Hz
,
C=O), 148.7 (C
qua
), 148.6 (C
qua
), 142.5 (C
qua
), 138.7 (C
qua
), 136.4 (C
qua
), 134.7 (C
qua
),
133.4 (Cqua ), 132.5 (d, 4JPC = 2.7 Hz, 2 ×CHA ), 132.2 (2 ×CHA ), 132.1 (2 ×CHA ), 130.7
(C
qua
), 129.4 (2
×
CH
A
), 129.3 (2
×
CH
A
), 128.5 (2
×
CH
A
), 128.4 (2
×
CH
A
), 128.1
(
2×CHA
), 124.6 (2
×
CH
A
), 123.8 (2
×
CH
A
), 120.6 (2
×
CH
A
), 93.7 (d,
1
J
CP
= 116.4 Hz,
C
qua
), 21.2 (CH
3
Tol), 21.1 (CH
3
Tol) ppm.
31
P NMR (162 MHz, CDCl
3
)
δ
30.9 ppm. FTIR
(nea )
νmax
: 3330 (NH), 1667 (C=O
s
), 1606 (C=C), 1204 (P=O) cm
−1
. HRMS (ESI-TOF) m/z:
[M+H]+calcd o C36H30N4O4P 613.2005, Found 613.2025.
P ocedu e o he Func ionaliza ion o γ-Lac am 5a wi h Me hyl Iodide
A solu ion o 5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-2H-py ol-2-one (
5a
)
(354 mg, 1mmol) in THF (1 mL) was added o a solu ion o eshly p epa ed LDA (1.2 mmol)
in e ahyd o u an (2 mL) a
−
78
◦
C. A e 1 h, an excess o me hyl iodide (93
µ
L, 1.5 mmol)
was added. The eac ion mix u e was s i ed o e nigh a
−
78
◦
C and was hen quenched
wi h a 0.5 M aqueous solu ion o HCl (10 mL). The eac ion mix u e was ex ac ed wi h
dichlo ome hane (2
×
10 mL) and he combined o ganic laye s we e washed wi h wa e
(2
×
10 mL), d ied wi h MgSO
4
, and concen a ed unde acuum. The c ude esidue
was pu i ied by ch oma og aphy (Hexanes), a o ding a 3:1 mix u e o 18 and 19 ha was
isola ed as pu e a e ch oma og aphy ollowed by c ys alliza ion (E 2O/Pen ane).
4-me hyl-5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-2H-py ol-2-one (
18
). The
p ocedu e was ollowed, a o ding 0.188 g (51%) o
18
as whi e c ys als. M.p. (E
2
O/Pen ane)
= 191–192
◦
C.
1
H NMR (400 MHz, CDCl
3
)
δ
7.40 (d,
3
J
HH
= 8.5 Hz, 2H,
2×CHA
),
7.35–7.20
(m, 5H, 5
×
CH
A
), 7.05 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 7.05 (d,
3
J
HH
= 8.5 Hz, 2H,
2×CHA
), 6.78 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 5.94 (s, 1H, NH), 5.33 (s, 1H, CH), 2.28
(s, 3H, CH
3
Tol), 2.24 (s, 3H, CH
3
Tol), 1.60 (s, 3H, CH
3
) ppm.
13
C NMR {
1
H} (101 MHz,
CDCl
3
)
δ
168.2 (C=O), 139.7 (C
qua
), 137.3 (C
qua
), 135.2 (C
qua
), 134.2 (C
qua
), 130.8 (C
qua
),
129.7 (C
qua
), 129.6 (2
×
CH
A
), 129.5 (2
×
CH
A
), 129.1 (2
×
CH
A
), 128.4 (CH
A
), 127.2
(2
×
CH
A
), 125.7 (C
qua
), 121.4 (2
×
CH
A
), 118.8 (2
×
CH
A
), 67.6 (CH), 21.0 (CH
3
Tol),
20.8 (CH
3
Tol), 13.6 (CH
3
) ppm. FTIR (nea )
νmax
: 3306 (NH
s
), 1688 (C=O
s
), 1608 (C=C
s
)
cm−1. HRMS (ESI-TOF) m/z: [M+H]+calcd o C25H25N2O 369.1967, Found 369.1973.
3-Hyd oxy-4-me hyl-5-phenyl-1-(p- olyl)-1,5-dihyd o-2H-py ol-2-one (
19
). The p oce-
du e was ollowed, a o ding 76 mg (26%) o
19
o as a pale yellow oil.
1
H NMR (400 MHz,
CDCl
3
)
δ
7.34 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 7.33–7.24 (m, 3H, 3
×
CH
A
), 7.16 (d,
3JHH = 8.3 Hz
, 2H, 2
×
CH
A
), 7.04 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 6.15 (s, 1H, OH), 5.26
Molecules 2022,27, 3624 19 o 25
(s, 1H, CH), 2.23 (s, 3H, CH
3
Tol), 1.73 (s, 3H, CH
3
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
166.9 (C=O), 140.7 (C
qua
), 136.2 (C
qua
), 134.8 (C
qua
), 134.6 (C
qua
), 129.6 (
2×CHA
), 129.1
(2
×
CH
A
), 128.5 (CH
A
), 127.3 (2
×
CH
A
), 122.1 (C
qua
), 121.3 (2
×
CH
A
), 66.0 (CH),
21.0 (CH
3
Tol), 9.5 (CH
3
) ppm. FTIR (nea )
νmax
: 3501 (OH
s
), 1681 (C=O
s
), 1607 (
C=C s
)
cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o C
18
H
18
N
2
O 280.1338, Found 280.1343.
Addi ionally, subs a e
18
can be ob ained in 95% yield om
17
by e luxing in a mix u e o
THF 1 (mL) and a 0.1 M aqueous solu ion o HCl (1 mL) o 1 h.
P ocedu e o he Vinylogous Mannich Reac ion o γ-Lac am 5b wi h E hyl Glyoxala e
A solu ion o e hyl 5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ole-2-ca boxyla e
(
5b
)(350 mg, 1 mmol), N,N-dime hylme hyleneiminium iodide (370 mg, 2 mmol) and
ie hylamine (350
µ
L, 2.5 mmol, in chlo o o m (3 mL) was e luxed o e nigh . The eac ion
mix u e was hen acidi ied wi h a 0.5 M aqueous solu ion o HCl (10 mL) and ex ac ed
wi h dichlo ome hane (2
×
10 mL). The combined o ganic laye s we e washed wi h wa e
(2
×
10 mL), d ied o e MgSO
4
, and concen a ed unde acuum. The c ude esidue was
pu i ied by c ys alliza ion om a mix u e o dichlo ome hane/hexanes (1:3), a o ding he
pu e unc ionalized γ-lac am de i a i e 20.
E hyl 2-((dime hylamino)me hyl)-5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-
py ole-2-ca boxyla e (
20
). The p ocedu e was ollowed, a o ding 321 mg (68%) o
20
as yellow c ys als. M.p. (Dichlo ome hane/Hexanes) = 170–172
◦
C.
1
H NMR (400 MHz,
CDCl
3
)
δ
7.25 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 7.20 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
),
7.13 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 7.00 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 6.65 (s, 1H,
NH), 5.95 (s, 1H, CH), 4.30–4.09 (m, 2H, CH
2
), 3.17 (d,
2
J
HH
= 14.0 Hz, 1H, C
HA
CH
B
), 2.74
(d,
2
J
HH
= 14.0 Hz, 1H, CH
A
C
HB
), 2.36 (s, 3H, CH
3
Tol), 2.31 (s, 3H, CH
3
Tol), 2.16 (s, 6H,
2×NCH3
), 1.24 ( ,
3
J
HH
= 7.1 Hz, 3H, CH
3
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
171.1
(C=O), 168.3 (C=O), 138.8 (C
qua
), 136.6 (C
qua
), 134.1 (C
qua
), 133.7 (C
qua
), 130.1 (C
qua
),
130.0 (2
×
CH
A
), 129.7 (2
×
CH
A
), 125.6 (2
×
CH
A
), 116.9 (2
×
CH
A
), 104.9 (CH
A
), 72.7
(CH), 62.1 (CH
2
O), 60.9 (CH
2
), 47.8 (2
×
NCH
3
), 21.2 (CH
3
, Tol), 20.8 (CH
3
, Tol), 14.2 (CH
3
,
OE ) ppm. FTIR (nea )
νmax
: 3312 (=CH
s
), 1691 (C=O
s
), 1615 (C=C
s
) cm
−1
. HRMS
(ESI-TOF) m/z: [M+H]+-Me2N calcd o C25H23N2O 367.1801, Found 367.1806.
P ocedu e o he Hyd ogena ion Reac ion o γ-Lac am 5b
A solu ion o e hyl 5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ole-2- ca -
boxyla e (
5b
) (350 mg, 1mmol) in E OH (5 mL) was s i ed o 2 days unde H
2
p essu e
(80 psi) in he p esence o palladium on ca bon (10%) (320 mg, 10% mmol). The eac ion
mix u e was il e ed h ough celi e and concen a ed unde acuum. The c ude esidue
was pu i ied by c ys alliza ion om a mix u e o E
2
O/Pen ane 1:3, a o ding pu e
21
as
whi e c ys als
E hyl (2S*,4S*)-5-oxo-1-(p- olyl)-4-(p- olylamino)py olidine-2-ca boxyla e (
21
). The
p ocedu e was ollowed, a o ding 326 mg (93%) o
21
as whi e c ys als M.p. (E
2
O/Pen ane)
= 142–144
◦
C.
1
H NMR (400 MHz, CDCl
3
)
δ
7.35 (d,
3
J
HH
= 8.5 Hz, 2H, 2
×
CH
A
), 7.18 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 7.03 (d,
3
J
HH
= 8.2 Hz, 2H, 2
×
CH
A
), 6.62 (d,
3JHH = 8.5 Hz
,
2H, 2
×
CH
A
), 4.78 (dd,
3
J
HH
= 7.7 Hz,
3
J
HH
= 7.7 Hz, 1H, CH), 4.16 (dd,
3
J
HH
= 8.3 Hz,
3
J
HH
= 8.3 Hz, 1H, CH), 4.10 (m, 2H, CH
2
O), 3.09 (m, 1H, CH
2
), 2.33 (s, 3H, CH
3
Tol),
2.26 (s, 3H, CH
3
Tol), 2.08 (m„ 1H, CH
2
), 1.12 (m, 3H, CH
3
OE ) ppm.
13
C NMR {
1
H}
(101 MHz, CDCl
3
)
δ
172.4 (C=O), 171.0 (C=O), 144.7 (C
qua
), 136.1 (C
qua
), 135.2 (C
qua
),
130.0 (
2×CHA
), 129.7 (2
×
CH
A
), 128.1 (C
qua
), 122.1 (2
×
CH
A
), 114.0 (2
×
CH
A
), 61.9
(CH
2
), 59.1 (CH), 55.4 (CH), 33.1 (CH
2
), 21.1 (CH
3
Tol), 20.5 (CH
3
Tol), 14.1 (CH
3
) ppm. FTIR
(nea )
νmax
: 3306 (N-H), 1748 (C=O), 1686 (C=O) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o C21H24NO3353.1865, Found 353.1862.
Molecules 2022,27, 3624 20 o 25
P ocedu e o he [3+3] Annula ion Reac ion o γ-Lac am 5b and β,γ-Unsa u a ed
Ke oes e 22
A solu ion o 5-oxo-1-(p- olyl)-4-(p- olylamino)-2,5-dihyd o-1H-py ole- 2-ca boxyla e
(
5b
) (350 mg, 1 mmol), Yb(OT )
3
(62.0 mg, 0.1 mmol) and
β
,
γ
–unsa u a ed ke oes e
22
(282 mg, 1.2 mmol) was s i ed in CH
2
Cl
2
a oom empe a u e o 6 h. The esul ing
mix u e was il e ed h ough celi e and concen a ed unde acuum. The c ude esidue
was pu i ied by column ch oma og aphy (Hexanes/AcOE (8:2), a o ding pu e
23
as a
whi e solid.
5-E hyl 2-me hyl (4S*,5S*)-4-(4-ni ophenyl)-7-oxo-1,6-di-p- olyl-4,5,6,7- e ahyd o-
1H-py olo[3,4-b]py idine-2,5-dica boxyla e (
23
). The p ocedu e was ollowed, a o ding
504 mg (89%) o
23
as a whi e solid.
1
H NMR (400 MHz, CDCl
3
)
δ
8.23 (d,
3
J
HH
= 8.7 Hz, 2H,
2×CHA
), 7.52 (d,
3
J
HH
= 8.7 Hz, 2H,
2×CHA
), 7.34 (d,
3
J
HH
= 8.2 Hz, 2H,
2×CHA
),
7.27 (d,
3
J
HH
= 8.0 Hz, 2H, 2
×
CH
A
), 7.18 (d,
3
J
HH
= 8.0 Hz, 2H, 2
×
CH
A
), 7.06 (d,
3JHH = 8.2 Hz
, 2H, 2
×
CH
A
), 5.76 (d,
3
J
HH
= 4.7 Hz, 1H, CH), 5.03 (s, 1H, CH), 4.91 (d,
3
J
HH
= 4.7 Hz, 1H, CH), 3.49 (s, 3H, OCH
3
), 3.34 (m, 1H, CH
2
O), 3.11 (m, 1H, C
H2
O), 2.36
(s, 3H, CH
3
Tol), 2.25 (s, 3H, CH
3
Tol), 0.79 (dd,
3
J
HH
= 7.1 Hz,
3
J
HH
= 7.1 Hz, 3H, CH
3
OE )
ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
167.8 (C=O), 163.6 (C=O), 163.0 (C=O), 149.8
(C
qua
), 147.4 (C
qua
), 138.2 (C
qua
), 137.9 (C
qua
), 136.1 (C
qua
), 135.8 (C
qua
), 135.2 (C
qua
),
134.6 (C
qua
), 129.7 (2
×
CH
A
), 129.2 (2
×
CH
A
), 129.2 (2
×
CH
A
), 128.6 (2
×
CH
A
), 124.1
(2
×
CH
A
), 121.0 (2
×
CH
A
), 119.6 (C
qua
), 113.4 (CH), 63.1 (CH), 61.9 (CH
2
), 52.3 (OCH
3
),
41.0 (CH), 21.4 (CH
3
Tol), 20.8 (CH
3
Tol), 13.6 (CH
3
) ppm. FTIR (nea )
νmax
: 3053 (=CH
s
),
1739 (C=O), 1723 (C=O), 1676 (C=O), 1622 (C=C) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o C32H29N33O7568.2084, Found 568.2078.
Gene al P ocedu e o he Nucleophilic Addi ion o O ganoli hium Reagen s o
γ
-Lac ams
5
A 1.6 M solu ion o he co esponding o ganoli hium eagen in hexanes (1.25 mL,
2 mmol) was added o a solu ion o he co esponding
γ
-lac am
5
(1 mmol) in e ahyd o-
u an (3 mL) a
−
78
◦
C unde N
2
a mosphe e. The eac ion was wa med o o e nigh .
The eac ion c ude was quenched wi h a 0.5 M aqueous solu ion o HCl (5 mL), and ex-
ac ed wi h dichlo ome hane (2
×
10 mL). The combined o ganic laye s we e washed wi h
wa e , d ied o e MgSO
4
, and concen a ed unde educed p essu e. The c ude esidue
was pu i ied by c ys alliza ion, p o iding he pu e unc ionalized
γ
-lac am de i a i es
25
.
In some cases, a p e ious pu i ica ion by ch oma og aphy was necessa y as de ailed o
each compound.
3-Me hyl-5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,3-dihyd o-2H-py ol-2-one (
25a
). The
gene al p ocedu e was ollowed, using 5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-
2H-py ol-2-one (354 mg, 1 mmol) (
5a
) and a 1.6 M solu ion o me hylli hium in hexanes
(1.25 mL, 2 mmol), a o ding 288 mg (78%) o
25a
as yellow c ys als a e ch oma og aphy
(Hexanes/AcOE 8:2) and subsequen c ys alliza ion (E
2
O/Pen ane 1:3). M.p. (E
2
O
/Pen ane) = 183–185
◦
C.
1
H NMR (400 MHz, CDCl
3
)
δ
7.31–7.25 (m, 4H, 4
×
CH
A
),
7.24–7.20
(m, 2H, 2
×
CH
A
), 7.11 (d,
3
J
HH
= 8.1 Hz, 2H, 2
×
CH
A
), 7.03–6.95 (m, 6H,
5×CHA + NH
), 5.63 (s, 1H, =CH), 2.33 (s, 3H, CH
3
Tol), 2.28 (s, 3H, CH
3
Tol), 1.45 (s, 3H,
CH
3
) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
175.4 (C
qua
), 165.6 (C=O), 148.9 (C
qua
),
137.1 (C
qua
), 135.6 (C
qua
), 133.1 (C
qua
), 131.9 (C
qua
), 130.0 (CH
A
), 129.6 (2
×
CH
A
),
129.4 (
2×CHA
), 128.6 (2
×
CH
A
), 128.3 (2
×
CH
A
), 127.3 (2
×
CH
A
), 121.8 (2
×
CH
A
),
94.8 (=CH), 92.8 (C
qua
), 25.3 (CH
3
), 21.1 (CH
3
Tol), 21.1 (CH
3
Tol) ppm. FTIR (nea )
νmax
:
3403 (NH
s
), 3053 (=CH
s
), 1674 (C=O
s
) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o
C25H25N2O 369.1967, Found 369.1972.
3-Bu yl-5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,3-dihyd o-2H-py ol-2-one (
25b
). The
gene al p ocedu e was ollowed, using 5-phenyl-1-(p- olyl)-3-(p- olylamino)-1,5-dihyd o-
2H-py ol-2-one (0.354 g, 1 mmol) (
5a
) and a 1.6 M solu ion o n-bu ylli hium in hexanes
(1.25 mL, 2 mmol), a o ding 300 mg (73%) o
25b
as an o ange oil a e ch oma og aphy
(Hexanes/AcOE 8:2).
1
H NMR (400 MHz, CDCl
3
)
δ
7.34–7.16 (m, 6H, 6
×
CH
A
), 7.11 (d,
3
J
HH
= 8.3 Hz, 2H, 2
×
CH
A
), 7.05–6.95 (m, 6H, 5
×
CH
A
+ NH), 5.61 (s, 1H, =CH), 2.33 (s,
Molecules 2022,27, 3624 21 o 25
3H, CH
3
Tol), 2.29 (s, 3H, CH
3
Tol), 2.12 (m, 1H, C
HA
H
B
), 1.85 (m, 1H, CH
AHB
), 1.36–1.00
(m, 4H, 2
×
CH
2
Bu), 0.76 ( ,
3
J
HH
= 6.9 Hz, 3H, CH
3
Bu) ppm.
13
C NMR {
1
H} (101 MHz,
CDCl
3
)
δ
175.0 (C
qua
), 166.6 (C=O), 148.6 (C
qua
), 136.2 (C
qua
), 135.2 (C
qua
), 133.0 (C
qua
),
131.9 (C
qua
), 129.9 (CH
A
), 129.5 (2
×
CH
A
), 129.2 (2
×
CH
A
), 128.6 (2
×
CH
A
), 128.2
(
2×CHA
), 127.0 (2
×
CH
A
), 121.9 (2
×
CH
A
), 95.5 (=CH), 95.0 (C
qua
), 38.0 (CH
2
Bu), 25.0
(CH
2
Bu), 22.6 (CH
2
Bu), 21.1 (CH
3
Tol), 21.0 (CH
3
Tol), 14.1 (CH
3
Bu) ppm. FTIR (nea )
νmax
:
3411 (NH
s
), 3053 (=CH
s
), 1703 (C=O
s
) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
calcd o
C28H31N2O 411.2436, Found 411.2442.
3-Bu yl-1-(4-me hoxyphenyl)-3-((4-me hoxyphenyl)amino)-5-phenyl-1,3-dihyd o-2H-
py ol-2-one (
25c
). The gene al p ocedu e was ollowed, using 1-(4-me hoxyphenyl)-3-((4-
me hoxyphenyl)amino)-5-phenyl-1,5-dihyd o-2H-py ol-2-one (386 mg, 1 mmol) (
5c
) and
a 1.6 M solu ion o n-bu ylli hium in hexanes (1.25 mL, 2 mmol), a o ding 296 mg (67%)
o
25c
as an o ange oil a e ch oma og aphy (Hexanes/AcOE 7:3).
1
H NMR (400 MHz,
CDCl
3
)
δ
7.34–7.20 (m, 6H, 5
×
CH
A
+ NH), 7.06 (d,
3
J
HH
= 8.8 Hz, 2H, 2
×
CH
A
), 7.05 (d,
3
J
HH
= 8.8 Hz, 2H, 2
×
CH
A
), 6.87 (d,
3
J
HH
= 8.8 Hz, 2H, 2
×
CH
A
), 6.74 (d,
3
J
HH
= 8.8 Hz,
2H, 2
×
CH
A
), 5.63 (s, 1H, =CH), 3.79 (s, 3H, OCH
3
), 3.77 (s, 3H, OCH
3
), 2.08 (m, 1H,
C
HA
H
B
), 1.82 (m, 1H, CH
AHB
), 1.31–1.07 (m, 4H, 2
×
CH
2
Bu), 0.77 ( ,
3
J
HH
= 6.8 Hz, 3H,
CH3Bu) ppm. 13C NMR {1H} (101 MHz, CDCl3)δ174.4 (Cqua ), 167.4 (C=O), 157.7 (Cqua ),
156.4 (C
qua
), 143.6 (C
qua
), 131.5 (C
qua
), 131.4 (C
qua
), 130.2 (CH
A
), 128.7 (2
×
CH
A
), 128.7
(2
×
CH
A
), 128.4 (2
×
CH
A
), 123.1 (2
×
CH
A
), 114.3 (2
×
CH
A
), 113.9 (2
×
CH
A
), 95.1
(C
qua
), 94.8 (=CH), 55.6 (OCH
3
), 55.5 (OCH
3
), 37.9 (CH
2
Bu), 25.1 (CH
2
Bu), 22.7 (CH
2
Bu),
14.1 (CH
3
Bu) ppm. FTIR (nea )
νmax
: 3391 (NH
s
), 3047 (=CH
s
), 1693 (C=O
s
) cm
−1
.
HRMS (ESI-TOF) m/z: [M+H]+calcd o C28H31N2O3443.2335, Found 443.2334.
1-(4-B omophenyl)-3-((4-b omophenyl)amino)-3-bu yl-5-phenyl-1,3-dihyd o-2H-py ol-
2-one (
25d
). The gene al p ocedu e was ollowed, using 1-(4-b omophenyl)-3-
((4-b omophenyl)amino)-5-phenyl-1,5-dihyd o-2H-py ol-2-one (
5d
) (484 mg, 1 mmol)
and a 1.6 M solu ion o n-bu ylli hium in hexanes (1.25 mL, 2 mmol), a o ding 411 mg
(76%) o
25d
as yellow c ys als a e ch oma og aphy (Hexanes/AcOE 85:15) ollowed by
c ys alliza ion (E
2
O /Pen ane 1:3). M.p. (E
2
O /Pen ane) = 129–130
◦
C.
1
H NMR (400 MHz,
CDCl
3
)
δ
7.42 (d,
3
J
HH
= 8.7 Hz, 2H, 2
×
CH
A
), 7.34–7.10 (m, 10H, 9
×
CH
A
+ NH), 6.94
(d,
3
J
HH
= 8.7 Hz, 2H, 2
×
CH
A
), 5.55 (s, 1H, =CH), 1.37–1.03 (m, 5H, 5
×
CHBu), 0.87
(m, 1H, CHBu), 0.74 ( ,
3
J
HH
= 6.9 Hz, 3H, CH
3
Bu) ppm.
13
C NMR {
1
H} (75 MHz, CDCl
3
)
δ
175.3 (C
qua
), 167.5 (C=O), 150.6 (C
qua
), 138.8 (C
qua
), 132.1 (2
×
CH
A
), 131.5 (C
qua
),
130.5 (CH
A
), 128.8 (2
×
CH
A
), 128.7 (2
×
CH
A
), 128.6 (2
×
CH
A
), 127.3 (2
×
CH
A
),
123.7 (
2×CHA
), 116.8 (C
qua
), 108.2 (C
qua
), 95.5 (C
qua
), 94.9 (=CH), 37.9 (CH
2
Bu), 25.1
(CH
2
Bu), 22.7 (CH
2
Bu), 14.0 (CH
3
Bu) ppm. FTIR (nea )
νmax
: 3397 (NH
s
), 3056 (
=CH s
),
1692 (C=O
s
) cm
−1
. HRMS (ESI-TOF) m/z: [M+H]
+
-B , calcd o C
26
H
26
B N
2
O 463.1208,
Found 463.1215.
3-Bu yl-1-(3-chlo ophenyl)-3-((3-chlo ophenyl)amino)-5-phenyl-1,3-dihyd o-2H-py ol-
2-one (
25e
). The gene al p ocedu e was ollowed, using 1-(3-chlo ophenyl)-3-((3-chlo ophen
yl)amino)-5-phenyl-1,5-dihyd o-2H-py ol-2-one (
5e
) (395 mg, 1 mmol) and a 1.6 M so-
lu ion o n-bu ylli hium in hexanes (1.25 mL, 2 mmol), a o ding 338 mg (75%) o
25e
as
yellow c ys als a e ch oma og aphy (Hexanes/AcOE 85:15) ollowed by c ys alliza ion
(Dichlo ome hane/Hexanes 1:3). M.p. (Dichlo ome hane/Hexanes) = 50–51
◦
C.
1
H NMR
(400 MHz, CDCl
3
)
δ
7.39–7.21 (m, 7H, 7
×
CH
A
), 7.13–7.09 (m, 2H, 2
×
CH
A
), 7.08–7.02 (m,
2H, 2
×
CH
A
), 6.94–6.87 (m, 2H, 2
×
CH
A
), 5.57 (s, 1H, =CH), 2.05 (m, 1H, C
HA
H
B
), 1.86
(m, 1H, CH
AHB
), 1.32–1.02 (m, 4H, 2
×
CH
2
Bu), 0.75 ( ,
3
J
HH
= 7.0 Hz, 3H, CH
3
Bu) ppm.
13
C NMR {
1
H} (101 MHz, CDCl
3
)
δ
175.2 (C
qua
), 166.9 (C=O), 152.8 (C
qua
), 140.1 (C
qua
),
134.6 (C
qua
), 134.3 (C
qua
), 131.1 (C
qua
), 130.6 (CH
A
), 130.2 (CH
A
), 129.4 (CH
A
), 128.6
(
2×CHA
), 128.5 (2
×
CH
A
), 126.7 (CH
A
), 125.9 (CH
A
), 125.1 (CH
A
), 123.9 (CH
A
), 121.9
(CH
A
), 120.2 (CH
A
), 96.3 (C
qua
), 94.8 (=CH), 37.7 (CH
2
Bu), 24.9 (CH
2
Bu), 22.6 (CH
2
Bu),
13.9 (CH
3
Bu) ppm. FTIR (nea )
νmax
: 3391 (NH
s
), 3069 (=CH
s
), 1705 (C=O
s
) cm
−1
.
HRMS (ESI-TOF) m/z: [M+H]+calcd o C26H25Cl2N2O 451.1344, Found 451.1352.

Molecules 2022,27, 3624 22 o 25
3.2. Biology
3.2.1. Ma e ials
Reagen s and sol en s we e used as pu chased wi hou u he pu i ica ion. All
s ock solu ions o he in es iga ed compounds we e p epa ed by dissol ing he powe ed
ma e ials in app op ia e amoun s o Dime hylsul oxide (DMSO). The inal concen a ion o
DMSO ne e exceeded 5% ( / ) in eac ions. The s ock solu ion was s o ed a 5
◦
C un il i
was used.
3.2.2. Cell Cul u e
Human epi helial lung ca cinoma cells (A549) (ATCC
®
CCL-185
™
, ATCC-Manassas,
VA, Uni ed S a es) we e g own in Kaighn’s Modi ica ion o Ham’s F-12 Medium (ATCC
®
30-2004
™
, ATCC-Manassas, VA, Uni ed S a es) and lung ib oblas cells (MRC5) (ATCC
®
CCL-171
™
, ATCC-Manassas, VA, Uni ed S a es) we e g own in Eagle’s Minimum Essen-
ial Medium (EMEM, ATCC
®
30-2003
™
, ATCC-Manassas, VA, Uni ed S a es). Epi helial
o a y adenoca cinoma cells (SKOV3) (ATCC
®
HTB-77
™
, ATCC-Manassas, VA, Uni ed
S a es) we e g own in McCoy’s 5A medium (ATCC
®
30-2007
™
, ATCC-Manassas, VA,
Uni ed S a es). All o hem we e supplemen ed wi h 10% o e al bo ine se um (FBS)
(Sigma-Ald ich, Spain) and wi h 1% o NORMOCIN solu ion (The mo Fishe , Wal ham,
Massachuse s (MA), Uni ed S a es). Cells we e incuba ed a 37
◦
C and 5% CO
2
a mosphe e,
and we e spli e e y 3–4 days o main ain monolaye co e age. Fo cy o oxici y expe i-
men s, A549 and SKOV3 cells we e seeded in 96-well pla es a a densi y o
2.5–3 ×103cells
pe well and incuba ed o e nigh o achie e 70% o con luence a he ime o exposi ion o
he cy o oxic compound.
3.2.3. Cy o oxici y Assays
Cells we e exposed o di e en concen a ions o he cy o oxic compounds and we e
incuba ed o 48 h. Then, 10
µ
L o cell coun ing ki -8 was added in o each well o an
addi ional wo hou s incuba ion a 37
◦
C. The abso bance o each well was de e mined
by an Au oma ic Elisa Reade Sys em (The mo Scien i ic Mul iskan FC Au oma ic Elisa
Reade Sys em, The mo Scien i ic, Shangai, China) a 450 nm wa eleng h.
4. Conclusions
The B öns ed-acid-ca alyzed mul icomponen eac ion o amines, aldehydes, and py u-
a e de i a i es is a s aigh o wa d me hod o he syn hesis o 3-amino
α
,
β
-unsa u a ed
γ
-lac am de i a i es. Selec i e unc ionaliza ion a C-4 o C-5 o hose subs a es is easible,
making use o enamine chemis y o inylogous nucleophilic addi ions, while he addi ion
o o ganome allic species allows unc ionaliza ion a C-3. Rema kably, he inylogous
aldol eac ion wi h e hyl glyoxala e leads o he exclusi e o ma ion o he an i-adduc .
In addi ion, chi al- unc ionalized
γ
-lac ams a e excellen p ecu so s o dias e eoselec i e
syn he ic ans o ma ions. The hyd ogena ion o he enamine moie y p oceeds wi h high
deg ee o syn dias e eoselec i i y, leading o he sa u a ed subs a es sui able o he u -
he p epa a ion o bicyclic compounds h ough in amolecula eac ions. In addi ion, an
example o a o mal [3+3] annula ion eac ion is desc ibed wi h high cis s e eocon ol. Mo e-
o e , some o he ob ained
γ
-lac am de i a i es showed
in i o
cy o oxici y, inhibi ing he
g ow h o human umo cells SKOV3 (human o a ian ca cinoma) and A549 (ca cinomic
human al eola basal epi helial cell) wi h selec i i y owa d MRC5 non-malignan lung i-
b oblas s. Al hough none o he subs a es we e p o ed o be supe io o chemo he apeu ic
agen Doxo ubicin, subs a e 12b showed a p omising 3.6 µM IC50 alue in A549 cell line,
whe eas he bes esul in SKOV3 cell line, 4.64 µM, was measu ed o compound 25e.
Molecules 2022,27, 3624 23 o 25
Supplemen a y Ma e ials:
The ollowing suppo ing in o ma ion can be downloaded a : h ps://
www.mdpi.com/a icle/10.3390/molecules27113624/s1,
1
H,
13
C,
19
F and
31
P-NMR and 2D NMR
copies o compounds
7
–
10
,
12
–
13
,
18
–
21
,
23
and
25
, c ys al da a o compounds
12b
and
13
and
Lipinsky alues.
Au ho Con ibu ions:
Concep ualiza ion, A.L.-F., X.d.C., Z.S.-B., E.M.d.M., F.P. and J.V.; me hod-
ology, A.L.-F., X.d.C. and Z.S.-B.; so wa e, A.L.-F., X.d.C. and Z.S.-B.; alida ion, E.M.d.M. and
J.V.; o mal analysis, A.L.-F., X.d.C. and Z.S.-B.; in es iga ion, A.L.-F., X.d.C. and Z.S.-B.; esou ces,
E.M.d.M., F.P. and J.V.; da a cu a ion, A.L.-F., X.d.C. and Z.S.-B.; w i ing—o iginal d a p epa a-
ion, J.V.; w i ing— e iew and edi ing, A.L.-F., X.d.C., Z.S.-B., E.M.d.M., F.P. and J.V.; isualiza ion,
E.M.d.M., F.P. and J.V.; supe ision, E.M.d.M. and J.V.; p ojec adminis a ion, E.M.d.M. and J.V.;
unding acquisi ion, E.M.d.M., F.P. and J.V. All au ho s ha e ead and ag eed o he published e sion
o he manusc ip .
Funding:
Financial suppo by Minis e io de Economía, Indus ia y Compe i idad (RTI2018-101818-
B-I00) and Gobie no Vasco (GV, IT 992-16) is g a e ully acknowledged. X.d.C. and A.L.-F. hank he
Basque Coun y Go e nmen o a p edoc o al g an .
Ins i u ional Re iew Boa d S a emen : No applicable.
In o med Consen S a emen : No applicable.
Da a A ailabili y S a emen :
The da a p esen ed in his s udy a e a ailable in he supplemen a y
ma e ials ile o on eques om he co esponding au ho (
1
H,
13
C,
19
F, and
31
P-NMR and HRMS
spec a and cy o oxici y essays).
Acknowledgmen s:
The au ho s gi e hanks o echnical and human suppo p o ided by SGIke
(UPV/EHU/ERDF, EU).
Con lic s o In e es : The au ho s decla e no con lic o in e es .
Sample A ailabili y: Samples o he compounds a e no a ailable.
Re e ences
1.
Ca uano, J.; Muccioli, G.G.; Robie e, R. Biologically ac i e
γ
-lac ams: Syn hesis and na u al sou ces. O g. Biomol. Chem.
2016
,14,
10134–10156. [C ossRe ] [PubMed]
2.
Saldí a -González, F.I.; Lenci, E.; T abocchi, A.; Medina-F anco, J.L. Explo ing he Chemical Space and he Bioac i i y P o ile o
Lac ams: A Chemoin o ma ic S udy. RSC Ad . 2019,9, 27105–27116. [C ossRe ]
3.
Ye, L.-W.; Shua, C.; Gagosz, F. Recen p og ess owa ds ansi ion me al-ca alyzed syn hesis o
γ
-lac ams. O g. Biomol. Chem.
2014,12, 1833–1845. [C ossRe ] [PubMed]
4.
Kamme e , C.; P es a , G.; Madec, D.; Poli, G. Syn hesis o
γ
-Lac ams and
γ
-Lac ones ia In amolecula Pd-Ca alyzed Allylic
Alkyla ions. Acc. Chem. Res. 2014,47, 3439–3447. [C ossRe ] [PubMed]
5.
Ri as, F.; Ling, T. Ad ances owa d he Syn hesis o Func ionalized
γ
-Lac ams. O g. P ep. P oced. In .
2016
,48, 254–295. [C ossRe ]
6.
Ma inez de Ma igo a, E.; de los San os, J.; Ochoa de Re ana, A.M.; Vica io, J.; Palacios, F. Mul icomponen Reac ions in he
Syn hesis o γ-Lac ams. Syn hesis 2018,50, 4539–4554. [C ossRe ]
7.
Ma inez de Ma igo a, E.; de los San os, J.; Ochoa de Re ana, A.M.; Vica io, J.; Palacios, F. Mul icomponen eac ions (MCRs): A
use ul access o he syn hesis o benzo used γ-lac ams. Beils ein J. O g. Chem. 2019,150, 1065–1085. [C ossRe ]
8.
Pelkey, E.T.; Pelkey, S.J.; G ege , J.G. Chap e Six—Reac ions o 3-py olin-2-ones. Ad . He e ocycl. Chem.
2019
,128, 433–565.
[C ossRe ]
9.
del Co e, X.; Maes o, A.; Ma inez de Ma igo a, E.; Palacios, F.; Vica io, J. Enan ioselec i e syn hesis o unsa u a ed
γ
-lac ams
en Ta ge s in he e ocyclic sys ems. In Chemis y and P ope ies; A anasi, O.A., Gab iele, B., Me ino, P., Spinelli, D., Eds.; Socie à
Chimica I aliana: Rome, I aly, 2021; Volume 25, ISBN 978-88-94952-27-8, ISSN 1724-9449. [C ossRe ]
10.
del Co e, X.; López-F ancés, A.; Maes o, A.; Villa e-Bei ia, I.; Sainz-Ramos, M.; Ma ínez de Ma igo a, E.; Palacios, F.;
Alonso, C.
;
de los San os, J.M.; Ped az, J.L.; e al. Mul icomponen Syn hesis o Unsa u a ed
γ
-Lac am De i a i es. Applica ions as
An ip oli e a i e Agen s h ough he Bioisos e ism App oach: Ca bonyl s. Phospho yl G oup. Pha maceu icals
2022
,15, 511.
[C ossRe ]
11.
del Co e, X.; López-F ancés, A.; Maes o, A.; Villa e-Bei ia, I.; Sainz-Ramos, M.; Ma ínez de Ma igo a, E.; Ped az, J.L.;
Vica io, J.
A Mul icomponen P o ocol o he Syn hesis o Highly Func ionalized
γ
-Lac am De i a i es and Thei Applica ions
as An ip oli e a i e Agen s. Pha maceu icals 2021,14, 782. [C ossRe ]
12.
del Co e, X.; López-F ancés, A.; de Ma igo a, E.M.; Palacios, F.; Vica io, J. S e eo- and Regioselec i e [3+3] Annula ion Reac ion
Ca alyzed by Y e bium: Syn hesis o Bicyclic 1,4-Dihyd opy idines. Ad . Syn h. Ca al. 2021,363, 4761–4771. [C ossRe ]
Molecules 2022,27, 3624 24 o 25
13.
Ki po ina, L.N.; Schepe kin, I.A.; Khlebniko , A.I.; Ruban, O.I.; Ge, Y.; Ye, R.D.; Kominsky, D.J.; Quinn, M.T. 4-A oyl-3-hyd oxy-
5-phenyl-1H-py ol-2(5H)-ones as N- o myl pep ide ecep o 1 (FPR1) an agonis s. Biochem. Pha macol.
2017
,142, 120–132.
[C ossRe ] [PubMed]
14.
Ma, K.; Wang, P.; Fu, W.; Wan, X.; Zhou, L.; Chu, Y.; Ye, D. Ra ional design o 2-py olinones as inhibi o s o HIV-1 in eg ase.
Bioo g. Med. Chem. Le . 2011,21, 6724–6727. [C ossRe ] [PubMed]
15.
Os e hage, C.; Kaminski, R.; König, G.M.; W igh , A.D. Ascosalipy olidinone A, an An imic obial Alkaloid, om he Obliga e
Ma ine Fungus Ascochy a salico niae.J. O g. Chem. 2000,65, 6412–6417. [C ossRe ] [PubMed]
16.
Pei e , C.; Selig, R.; Kinkel, K.; O , D.; To zke, F.; Schaech ele, C.; Heiden eich, R.; Roecken, M.; Schollmeye , D.; Lau e , S. Design,
Syn hesis, and Biological E alua ion o No el 3-A yl-4-(1H-indole-3yl)-1,5-dihyd o-2H-py ole-2-ones as Vascula Endo helial
G ow h Fac o Recep o (VEGF-R) Inhibi o s. J. Med. Chem. 2008,51, 3814–3824. [C ossRe ]
17.
Gao, H.; Sun, J.; Yan, C.-G. Syn hesis o unc ionalized 2-py olidinones ia domino eac ions o a ylamines, e hyl glyoxyla e and
ace ylenedica boxyla es. Te ahed on 2013,69, 589–594. [C ossRe ]
18.
Khan, A.T.; Gosh, A.; Khan, M.M. One-po ou -componen domino eac ion o he syn hesis o subs i u ed dihyd o-2-oxypy ole
ca alyzed by molecula iodine. Te ahed on Le . 2012,53, 2622–2626. [C ossRe ]
19.
Saha, M.; Das, A.R. Access o Di e se 2-Py olidinone, 3,4,5-Subs i u ed Fu anone and 2-Oxo-dihyd opy oles Applying G aphene
Oxide Nanoshee : Un a eling o Sol en Selec i i y. Chemis ySelec 2017,2, 10249–10260. [C ossRe ]
20.
del Co e, X.; Ma inez de Ma igo a, E.; Palacios, F.; Vica io, J. A B øns ed Acid-Ca alyzed Mul icomponen Reac ion o he
Syn hesis o Highly Func ionalized γ-Lac am De i a i es. Molecules 2019,24, 2951. [C ossRe ]
21.
Palacios, F.; Vica io, J.; Apa icio, D. An e icien syn hesis o achi al and chi al cyclic dehyd o-
α
-amino acid de i a i es h ough
nucleophilic addi ion o Amines o β,γ-unsa u a ed α-ke o es e s. Eu . J. O g. Chem. 2006, 2843–2850. [C ossRe ]
22.
Li, X.; Deng, H.; Luo, S.; Cheng, J.-P. O ganoca aly ic Th ee-Componen Reac ions o Py u a e, Aldehyde and Aniline by
Hyd ogen-Bonding Ca alys s. Eu . J. O g. Chem. 2008, 4350–4356. [C ossRe ]
23.
Ghashang, M. 1-Bu yl-1-me hylpy olidinium hyd ogen sul a e-p omo ed p epa a ion o 1,5-dia yl-3-(a ylamino)-1H-py ol-
2(5H)-one de i a i es. Res. Chem. In e med. 2013,39, 2187–2195. [C ossRe ]
24.
del Co e, X.; Maes o, A.; Vica io, J.; Ma ínez de Ma igo a, E.; Palacios, F. B öns ed-Acid-Ca alyzed Asymme ic Th ee-
Componen Reac ion o Amines, Aldehydes, and Py u a e De i a i es. Enan ioselec i e Syn hesis o Highly Func ionalized
γ-Lac am De i a i es. O g. Le . 2018,20, 317–320. [C ossRe ] [PubMed]
25.
del Co e, X.; López-F ancés, A.; Maes o, A.; Ma inez de Ma igo a, E.; Palacios, F.; Vica io, J. B öns ed Acid Ca alyzed
Mul icomponen Syn hesis o Phospho a ed and Fluo ina ed
γ
-Lac am De i a i es. J. O g. Chem.
2020
,85, 14369–14383.
[C ossRe ]
26.
Zhu, J.; Wang, Q.; Wang, M.-X. (Eds.) Mul icomponen Reac ions in O ganic Syn hesis; Wiley-VCH: Weinheim, Ge many, 2014;
ISBN 978-3-527-67820-4.
27.
Mülle , T.J.J. Science o Syn hesis, Mul icomponen Reac ions; Thieme: S u ga , Ge many, 2014; Volumes 1 and 2,
ISBN 9783131668813 3131668814.
28.
Knapp, J.M.; Ku h, M.J.; Shaw, J.T.; Younai, A. Di e si y-O ien ed Syn hesis; T abocchi, A., Ed.; Willey: New Yo k, NY, USA, 2013;
pp. 29–57, ISBN 978-1-118-61814-1.
29.
Sch eibe , S.L. Ta ge -o ien ed and di e si y-o ien ed o ganic syn hesis in d ug disco e y. Science
2000
,287, 1964–1969. [C ossRe ]
30.
Khala , A.I.; Waigh, R.D.; D ummond, A.J.; P ingle, B.; McG oa y, I.; Skelle n, G.G.; Suckling, C.J. Dis amycin Analogues wi h
Enhanced Lipophilici y: Syn hesis and An imic obial Ac i i y. J. Med. Chem. 2004,47, 2133–2156. [C ossRe ]
31.
Ye, Y.; Fang, F.; Li, Y. Syn hesis and an i-bio ilm ac i i ies o dihyd o-py ol-2-one de i a i es on Pseudomonas ae uginosa.Bioo g.
Med. Chem. Le . 2015,25, 597–601. [C ossRe ]
32.
Zhu, Q.; Gao, L.; Chen, Z.; Zheng, S.; Shu, H.; Li, J.; Jiang, H.; Liu, S. A no el class o small-molecule caspase-3 inhibi o s p epa ed
by mul icomponen eac ions. Eu . J. Med. Chem. 2012,54, 232–238. [C ossRe ]
33.
Gein, V.L.; Popo , A.V.; Kolla, V.E.; Popo a, N.A.; Po emkin, K.D. Syn hesis and biological ac i i y o 1,5-dia yl-3-a ylamino-4-
ca boxyme hyl-2,5-dihyd o-2-py olones and 1,5-dia yl-4-ca boxyme hyl e ahyd opy ole-2, 3-diones. Pha m. Chem. J.
1993
,27,
343–346. [C ossRe ]
34.
Gein, V.L.; Popo , A.V.; Kolla, V.E.; Popo a, N.A. Syn hesis and biological ac i i y o 1,5-dia yl-3-alkylamino-4-ca boxyme hyl-
2,5-dihyd opy ol-2-ones and 1,5-dia yl-4-ca boxyme hyl- e ahyd opy ol-2,3-diones. Pha mazie 1993,48, 107–109. [C ossRe ]
35.
Yang, Y.; Lu, C.; Chen, M.; Chen, K.; Wu, Y.; Wu, S. Cy o oxic Polyke ides Con aining Te amic Acid Moie ies Isola ed om he
Fungus Mycelioph ho a The mophila: Elucida ion o he Rela ionship be ween Cy o oxici y and S e eocon igu a ion. Chem. Eu . J.
2007,13, 6985–6991. [C ossRe ] [PubMed]
36. Janecka, A.; Wy e, A.; Gach, K.; Fichna, J.; Janecki, T. Na u al and syn he ic α-me hylenelac ones and α-me hylenelac ams wi h
an icance po en ial. D ug Disco . Today 2012,17, 561–572. [C ossRe ] [PubMed]
37.
Hazuda, D.; Blau, C.U.; Felock, P.; Has ings, J.; P amanik, B.; Wol e, A.; Bushman, F.; Fa ne , C.; Goe z, M.; Williams, M.; e al.
Isola ion and Cha ac e iza ion o No el Human Immunode iciency Vi us In eg ase Inhibi o s om Fungal Me aboli es. An i i .
Chem. Chemo he . 1999,10, 63–70. [C ossRe ] [PubMed]
38.
Singh, S.B.; Goe z, M.A.; Jones, E.T.; Bills, G.F.; Giacobbe, R.A.; He anz, L.; S e ens-Miles, S.; Williams, D.L. O e omycin: A
No el An agonis o Endo helin Recep o . J. O g. Chem. 1995,60, 7040–7042. [C ossRe ]
Molecules 2022,27, 3624 25 o 25
39.
He, H.; Yang, H.Y.; Bigelis, R.; Solum, E.H.; G eens ein, M.; Ca e , G.T. Py ocidines A and B, new an ibio ics p oduced by a
ilamen ous ungus. Te ahed on Le . 2002,43, 1633–1636. [C ossRe ]
40.
Li, B.; We e , W.J.; Walsh, C.T.; Bowe s, A.A. Di hiolopy olones: Biosyn hesis, syn hesis, and ac i i y o a unique class o
disul ide-con aining an ibio ics. Na . P od. Rep. 2014,31, 905–9023. [C ossRe ]
41.
The Chemis y o Enols and Enamines. In O ganic Mechanisms: Reac ions, S e eochemis y and Syn hesis; Ha ma a, M., Ed.; Sp inge :
Be lin/Heidelbe g, Ge many, 2010; p. 487. [C ossRe ]
42.
Zhuang, C.; Miao, Z.; Zhu, L.; Dong, G.; Guo, Z.; Wang, S.; Zhang, Y.; Wu, Y.; Yao, J.; Sheng, C.; e al. Disco e y, Syn hesis, and
Biological E alua ion o O ally Ac i e Py olidone De i a i es as No el Inhibi o s o p53–MDM2 P o ein–P o ein In e ac ion. J.
Med. Chem. 2012,55, 9630–9642. [C ossRe ]
43.
Huang, W.; Dong, Z.; Wang, F.; Peng, H.; Liu, J.-Y.; Zhang, J.-T. A Small Molecule Compound Ta ge ing STAT3 DNA-Binding
Domain Inhibi s Cance Cell P oli e a ion, Mig a ion, and In asion. ACS Chem. Biol. 2014,9, 1188–1196. [C ossRe ]
44.
Ta na sky, S.S.; Dubinina, G.G.; Golo ach, S.M.; Ya moluk, S.M. An i umo ac i i y among de i a i es o he 3-chlo o-4-(3-
hyd oxyanilino)-2,5-dihyd opy ole-2,5-dione. Biopolym. Cell 2003,19, 548–552. [C ossRe ]
45.
Sánchez, C.; Zhu, L.; B aña, A.F.; Salas, A.P.; Roh , J.; Méndez, C.; Salas, J.A. Combina o ial biosyn hesis o an i umo indoloca -
bazole compounds. P oc. Na . Acad. Sci. USA 2005,102, 461–466. [C ossRe ]
46.
Cao, W.; Wang, Z.; Han, X.; Liu, J.; Wang, W.
In i o
cy o oxici y sc eening o iden i y no el an i-os eosa coma he apeu ics
a ge ing py u a e dehyd ogenase kinase 2. Bioo g. Med. Chem. Le . 2019,29, 126665. [C ossRe ] [PubMed]
47.
Joksimo i´c, N.; Pe onije i´c, J.; Janko i´c, N.; Baski´c, D.; Popo i´c, S.; Todo o i´c, D.; Ma i´c, S.; Bogdano i´c, G.A.; V aneš, M.;
To , A.; e al
. Syn hesis, cha ac e iza ion, an icance e alua ion and mechanisms o cy o oxic ac i i y o no el 3-hyd oxy-3-
py olin-2-ones bea ing henoyl agmen : DNA, BSA in e ac ions and molecula docking s udy. Bioo g. Chem.
2019
,88,
102954–102968. [C ossRe ] [PubMed]
48.
Yang, D.; Huang, C.; Liao, H.; Zhang, H.; Wu, S.; Zhu, Q.; Zhou, Z.-Z. Disco e y o Dihyd opy ol-2-ones as No el G0/G1-Phase
A es ing Agen s Inducing Apop osis. ACS Omega 2019,4, 17556–17560. [C ossRe ] [PubMed]
49.
Buchanan, G.S.; Dai, H.; Hsung, R.P.; Ge asyu o, A.I.; Schneinebeck, C.M. Asymme ic Aza-[3+3] Annula ion in he Syn hesis o
Indolizidines: An Unexpec ed Re e sal o Regiochemis y. O g. Le . 2011,13, 4402–4405. [C ossRe ]
50.
Li, P.; Vik, E.C.; Maie , J.M.; Ka ki, I.; S ickland, S.M.S.; Umana, J.M.; Smi h, M.D.; Pellechia, P.-J.; Shimizu, K.D. Elec os a ically
D i en CO−πA oma ic In e ac ions. J. Am. Chem. Soc. 2019,141, 12513–12517. [C ossRe ]
51.
Recio, R.; Vengu -Climen , E.; Mouillac, B.; O cel, H.; López-Láza o, M.; Calde ón-Mon año, J.M.; Ál a ez, E.; Khia , N.;
Fe nández, I. Design, syn hesis and biological s udies o a lib a y o NK1-Recep o Ligands Based on a 5-a yl hiosubs i u ed
2-amino-4,6-dia yl-3-cyano-4H-py an co e: Swi ch om an agonis o agonis e ec by chemical modi ica ion. Eu . J. Med. Chem.
2017,138, 644–660. [C ossRe ]
52. Ho sman, G.P.; Zechel, D.L. Phosphona e biochemis y. Chem. Re . 2017,117, 5704–5783. [C ossRe ]
53.
Mucha, A.; Ka a ski, P.; Be licki, L. Rema kable Po en ial o he Aminophosphona e /Phosphina e S uc u al Mo i in Medicinal
Chemis y. J. Med. Chem. 2011,54, 5955–5980. [C ossRe ]
54. Ka l, D.M. Phospho us, he S a o Li e. Na u e 2000,406, 31–33. [C ossRe ]
55. Engel, R. Handbook o O ganophospho us Chemis y; Ma cel Dekke Inc.: New Yo k, NY, USA, 1992; ISBN 9780429178092.
56.
Ka a ski, P.; Lejezak, B. Biological ac i i y o aminophosphonic acids. Phospho us Sul u Silicon Rela . Elem.
1991
,63, 193–215.
[C ossRe ]
57. Rida o olimus. D ugs R. D. 2010,10, 165–178. [C ossRe ] [PubMed]
58.
Ri e a, V.M.; Squillace, R.M.; Mille , D.; Be k, L.; Wa dwell, S.D.; Ning, Y.; Pollock, R.; Na asimhan, N.I.; Iuliucci, J.D.;
Wang, F.; e al
. Rida o olimus (AP23573; MK-8669), a Po en mTOR Inhibi o , Has B oad An i umo Ac i i y and Can Be
Op imally Adminis e ed Using In e mi en Dosing Regimens. Mol. Cance The . 2011,10, 1059–1071. [C ossRe ] [PubMed]
59. Ma kham, A. B iga inib: Fi s Global App o al. D ugs 2017,77, 1131–1135. [C ossRe ] [PubMed]
60.
Huang, W.-S.; Liu, S.; Zou, D.; Thomas, M.; Wang, Y.; Zhou, T.; Rome o, J.; Kohlmann, A.; Li, F.; Qi, J.; e al. Disco e y o B iga inib
(AP26113), a Phosphine Oxide-Con aining, Po en , O ally Ac i e Inhibi o o Anaplas ic Lymphoma Kinase. J. Med. Chem.
2016
,
59, 4948–4964. [C ossRe ]