New generation of enantiomerically pure N-α-carboxyalkylglycolurils

Article abstract of DOI:10.1016/j.mencom.2008.03.016

The title compounds have been synthesised by the α-ureidoalkylation of (S)-N-carbamoyl-α-amino acids with 1,3-dimethyl- and 1,3-dimethyl-4,5-diphenyl-4,5-dihydroxyimidazolidin-2-ones.

Full text of DOI:10.1016/j.mencom.2008.03.016

Mendeleev
Communications
Mendeleev Commun., 2008, 18, 96–98
New generation of enantiomerically pure N- -carboxyalkylglycolurils
Vladimir V. Baranov, Angelina N. Kravchenko,* Pavel A. Belyakov and Nina N. Makhova
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian
Federation. Fax: +7 499 135 5328; e-mail: kani@server.ioc.ac.ru
DOI: 10.1016/j.mencom.2008.03.016
The title compounds have been synthesised by the -ureidoalkylation of (S)-N-carbamoyl- -amino acids with 1,3-dimethyl- and
1,3-dimethyl-4,5-diphenyl-4,5-dihydroxyimidazolidin-2-ones.
2,4,6,8-Tetraalkyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3.7-diones
(2,4,6,8-tetraalkylglycolurils) possess the highest psychotropic
activity among bicyclic bisureas.1 Furthermore, there are com-
pounds of this class that are currently at various stages of
adoption to medical practice, including Mebicarum, a well-
known day-time tranquillizer.2 The incorporation of a carboxy-
propyl moiety at a glycoluril nitrogen atom gives rise to anxiolytic
and antihypoxic properties (even in racemates) comparable to
similar effects of Mebicarum.3 Therefore, the simultaneous
incorporation of carboxyalkyl and alkyl moieties into a glycoluril
molecule may enhance these types of activity. On the other
hand, racemic glycolurils with phenyl groups at the C(1) and
C(5) bridging atoms exhibit another type of activity, viz., they
affect the monooxygenase system of liver,4 though they are not
very efficient. Thus, it was of interest to synthesise glycolurils
that combine alkyl, phenyl and carboxyalkyl substituents in a
molecule. As a rule, only one enantiomer in racemic pharma-
Table 1 Dependence of the yields and diastereomeric ratios of glycolurils
on the amount of HCl used.
Amount of HCl
(molar equiv.)
Diastereomeric ratio
3:3' and 4:4'
Reagents
Yield (%)
1a, 2a
0.5
1
3a:3'a, 1:1
3a:3'a, 1.5:1
25
20
1b, 2a
1c, 2a
1a, 2b
1b, 2b
1d, 2b
1e, 2b
0.5
1
3b:3'b, 1.5:1
3b:3'b, 3.5:1
3c:3'c, 5:1
Stereoisomer 3c
4a:4'a, 1:1
4a:4'a, 2.5:1
Stereoisomer 4b
Stereoisomer 4b
4c:4'c, 1:1
4c:4'c, 3:1
4d:4'd, 1:1
4d:4'd, 2:1
37
25
0.5
1
10
8
0.5
1
88
80
0.5
1
91
83
0.5
1
16
10
0.5
1
74
70
ceutical compounds is useful.5 This study aims at synthesising
glycolurils of a new type whose molecules contain N-alkyl,
phenyl and (S)- -carboxyalkyl groups in various combinations.
R2
R2
NH2
NH
Me
Me
H
N
O
N
N
OH
OH
i–iii
+
O
O
O
R1
N
N
N
We have previously obtained enantiomerically pure N- -carboxy-
R2
R2
COOR3
COOH
Me
Me
alkylglycolurils containing neither phenyl nor alkyl substituents
by diastereoselective and diastereospecific cyclocondensations
of N-nonsubstituted 4,5-dihydroxyimidazolidin-2-one (DHI)
with (S)- and (R)-N-carbamoyl- -amino acids under acidic
catalysis conditions.6,7 Therefore, to synthesise a new genera-
tion of enantiomerically pure glycolurils, we studied the -ureido-
alkylation of (S)-N-carbamoyl- -amino acids (N-carbamoyl-
alanine 1a, N-carbamoyl- -aminobutyric acid 1b, N-carbamoyl-
norvaline 1c, N-carbamoylvaline 1d and N-carbamoylphenyl-
alanine 1e) using 1,3-dimethyl-DHI 2a and 1,3-dimethyl-4,5-
diphenyl-DHI 2b as ureidoalkylating reagents. The reactions
were carried out for 2–3 h in the presence of concentrated HCl
(from 0.5 to 2 mol) at 85–90 °C in various solvents. These
studies resulted in target glycolurils 3a–c and 4a–d (Scheme
1)† with various diastereomeric compositions (Table 1). Water or
an H2O–PriOH mixture (1:1.5) were the best suitable solvents
for synthesising glycolurils 3a–c, while MeOH or an MeOH–
PriOH mixture (1:1) were the best solvents for obtaining
compounds 4a–d. Note that the use of MeOH in the syntheses
of glycolurils 4 resulted in the methyl esters of N- -carboxy-
alkylglycolurils 4a–d and 4'a,c,d due to the esterification of
carboxylic groups.‡
R1
3a–c, 4a–d
1a–e
2a,b
1: a R1 = Me
b R1 = Et
c R1 = Pr
2: a R2 = H
b R2 = Ph
d R1 = Pri
e R1 = Bn
R4
R2
Me
H
O
N
N
N
+
+
O
O
O
N
R5
N
N
R2
COOR3
Me
R4
R1
3'a–c, 4'a,c,d
5a–f
5: a R4 = H, R5 = Et
b R4 = H, R5 = Me
c R4 = H, R5 = Pr
d R4 = H, R5 = Pri
e R4 = H, R5 = Bn
f R4 = Me, R5 = H
3, 3': a R1 = Me, R2 = R3 = H
b R1 = Et, R2 = R3 = H
c R1 = Pr, R2 = R3 = H
4, 4': a R1 = Me, R2 = Ph, R3 = Me
b R1 = Et, R2 = Ph, R3 = Me
c R1 = Pri, R2 = Ph, R3 = Me
d R1 = Bn, R2 = Ph, R3 = Me
Scheme 1 Reagents and conditions: i, 1 mol 2a:0.5 mol HCl, H2O
or H2O + PriOH, 85–90 °C, 3 h (diastereoselective synthesis of 3a–c);
ii, 1 mol 2a:1 mol HCl, H2O or H2O + PriOH, 85–90 °C, 3 h (diastereo-
specific synthesis of 3c); iii, 1 mol 2:1 mol HCl, MeOH or MeOH + PriOH,
reflux, 2 h (diastereoselective synthesis of 4a,c,d or diastereospecific syn-
thesis of 4b).
†
The configurations of the CH–CH bridging carbon atoms in the bicyclic
system, viz., 1R,5R in the major diastereomer and 1S,5S in the minor
one, was assigned by analogy with monosubstituted N- -carboxyalkyl-
glycolurils obtained previously,6,7 based on the similarity of the H and
1
13C NMR spectra of compounds 3 and 4.
– 96 –
© 2008 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2008, 18, 96–98
The diastereomeric composition of the reaction products was
17 (17a)
6 (6a)
determined by 1H and 13C NMR spectroscopy. Glycolurils 3a,b
and 4a,c,d were formed as mixtures of two diastereomers 3a,b
and 3'a,b or 4a,c,d and 4'a,c,d; this was observed as doubling
of some proton signals. The signals of the CH protons in the
amino acid moiety of the major diastereomers are shifted down-
field with respect to similar signals of the minor diastereomers.
H 21 (21a)
N 4 (4a)
5 (5a)
1 (1a)
N
18 (18a)
O
O16 (16a)
7 (7a)
8 (8a)
3 (3a)
N
N 2 (2a)
12 (12a) 14 (14a)
9 (9a)
19 (19a)
COOH 15 (15a)
‡
All the new compounds exhibited satisfactory elemental analyses, and
11 (11a)
13 (13a)
1
10 (10a)
their structures were confirmed by H and 13C NMR spectroscopy. The
1H and 13C NMR spectra were recorded on Bruker WM-250 (250 MHz),
AM-300 (75.5 MHz) and DRX-500 (500 MHz) instruments. Chemical
shifts were measured with reference to the residual protons of [2H6]DMSO
as a solvent (d 2.50).
Melting points were determined in a Gallenkamp instrument (Sanyo).
Commercial compounds (benzene, amino acids, KOCN, diethylthio- and
dimethylureas) from Acros were used in the syntheses. The solvents were
used without preliminary purification. Starting N-carbamoyl- -amino acids
1a–e12,13 and DHIs 2a,b14,15 were synthesised as described in the literature.
3a/3'a
(1.5:1): yield 25%, mp 248–250 °C (MeOH). 1H NMR ([2H6]DMSO)
d: 5.11–5.28 (m, 2H CH–CH); diastereomer 3a: 1.40 (m, 3H, Me), 2.72
(s, 3H, Me), 2.62 (d, 3H, Me, J 7.5 Hz), 4.30 (m, 1H, CH), 8.12 (s, 1H,
NH); diastereomer 3'a: 4.11 (m, 1H, CH), 7.77 (s, 1H, NH).
3b/3'b (3.5:1): yield 37%, mp 295–297 °C (MeOH). 1H NMR
([2H6]DMSO) d: 0.85 [m, 3H, Me(11 + 11a)], 1.79 [m, 2H, CH2(10a)],
1.92 [m, 2H, CH2(10)], 2.63 [s, 3H, Me(17a)], 2.64 [s, 3H, Me(19a)],
2.72 [s, 3H, Me(17)], 2.74 [s, 3H, Me(19a)], 3.90 [m, 1H, CH(9)], 4.13
[dd, 1H, CH(9a), J 5 Hz], 5.13 [m, 2H, CH–CH(5 + 5a + 1 + 1a)], 7.77
[s, 1H, NH(21)], 7.85 [s, 1H, NH(21a)]. 13C{1H} NMR ([2H6]DMSO) d:
10.90 [Me(11)], 11.10 [Me(11a)], 21.51 [CH2(10a)], 23.10 [CH2(10)],
27.88 [NMe(17a)], 27.92 [NMe(17)], 29.68 [NMe(19a)], 30.27 [NMe(19)],
56.94 [CH(9)], 57.97 [CH(9a)], 66.13 [NCHN(5a)], 66.30 [NCHN(5)],
72.31 [NCHN(1a)], 72.44 [NCHN(1)], 158.14 [CO(7a)], 158.54 [CO(7)],
Figure 1 Atom numbering in the major and minor diastereomers of
3b + 3'b, which is used for the assignment of the signals of protons to
those of the carbon atoms based on the HSQC and HMBC spectra of these
compounds. A letter ‘a’ at the numbers of atoms signifies the same atoms
in the second isomer.
The signals in the 1H and 13C NMR spectra were assigned using
HSQC8 and HMBC9 techniques. The studies were carried out
for diastereomers 3b + 3'b using [2H6]DMSO as a solvent. The
HMBC spectrum shows cross peaks corresponding to the long-
range interactions of the protons at C(9) or C(9a) with the
carbon atoms of carbonyl groups C(3) or C(3a) and C(12) or
C(12a), respectively, and with just one cyclic carbon atom C(3)
or C(3a). The protons of the methyl groups at carbon atoms
C(17) or C(17a) and C(19) or C(19a) display cross peaks with
the corresponding carbon atom C(7) or C(7a) of the carbonyl
group. The protons of the Me group at carbon atom C(19) or
C(19a) manifest long-range interactions with the cyclic carbon
atom C(1) or C(1a), respectively, whereas the protons of the
methyl groups at C(17) or C(17a) manifest long-range interac-
tions with carbon atom C(5) or C(5a). Based on the HSQC and
HMBC spectra of compounds 3b + 3'b, we assigned the proton
signals to those of carbon atoms (Figure 1).
Analysis of the information-richest part of the spectra of the
test compounds (i.e., the area of the signals of the amino acid
moiety CH protons at d 3.7–4.5) shows that, depending on the
structure of the starting compounds and the molar amount of
HCl per mole of DHI 2a,b, the ratio of diastereomers 3a and
3'a varies from 1:1 to 1.5:1; for 3b and 3'b, from 1.5:1 to 3:1;
for 3c and 3'c, from 5:1 to 1:0; for 4a and 4'a, from 1:1 to
2.5:1; for 4c and 4'c, from 1:1 to 3:1; and for 4d and 4'd, from
1:1 to 2:1 (Table 1), which indicates that the reactions of DHI
2a with (S)-N-carbamoyl- -amino acids 1a–c and of DHI 2b
with (S)-N-carbamoyl- -amino acids 1a,d,e occur diastereo-
selectively. The reaction of DHI 2a with (S)-N-carbamoyl-
norvaline 1c in the presence of 1 mol of HCl and that of DHI 2b
with N-carbamoyl- -aminobutyric acid 1b in the presence of
either 0.5 or 1 mol of HCl result in one stereoisomer 3c or 4b,
respectively.
159.77 [CO(3a)], 160.02 [CO(3)], 172.49 [COOH(12)], 172.88 [COOH(12a)]
.
3c: yield 8%, mp 300–302 °C (MeOH), [a]D20 +71 (c 1.8, MeOH).
1H NMR ([2H6]DMSO) d: 0.89 (m, 3H, Me), 1.30 (m, 2H, CH2), 1.90
(m, 2H, CH2), 2.65 (s, 3H, Me), 2.78 (s, 3H, Me), 4.00 (m, 1H, CH),
5.11 (s, 2H, CH–CH), 7.79 (s, 1H, NH).
3c/3'c (5:1): yield 10%, mp 298–300 °C (MeOH). 1H NMR ([2H6]DMSO)
d: 0.81–0.89 (m, 3H, Me), 1.45–1.65 (m, 2H, CH2), 1.66–2.01 (m, 2H,
CH2), 2.63 (s, 3H, Me), 2.65 (s, 3H, Me), 2.81 (s, 3H, Me), 2.82 (s, 3H,
Me), 4.00 (m, 1H, CH), 4.48 (m, 1H, CH), 5.11 (s, 2H, CH–CH), 5.15
(s, 2H, CH–CH), 7.77 (s, 1H, NH), 7.85 (s, 1H, NH).
4a/4'a
(2.5:1): yield 88%, mp 138–140 °C (MeOH). 1H NMR ([2H6]DMSO)
d: 1.4 (d, 3H, CMe), 2.56 (s, 3H, NMe), 2.58 (s, 3H, NMe), 2.75 (s, 3H,
NMe), 2.80 (s, 3H, NMe), 3.61 (s, 3H, OMe), 3.68 (s, 3H, OMe), 3.91
(dd, 1H, CH, J 7 Hz), 4.08 (d, 1H, CH, J 7 Hz), 6.73–7.17 (m, 10H, Ph),
8.45 (s, 1H, NH), 8.51 (s, 1H, NH). 13C{1H} NMR ([2H6]DMSO) d: 16.00
(Me), 16.87 [Me(a)], 26.44 [NMe(a)], 26.79 (NMe), 28.78 [NMe(a)], 28.99
(NMe), 50.02 (CH), 51.27 [CH(a)], 52.29 (OMe), 83.18 [CPh(a)], 83.67
(CPh), 7.23 (CPh), 87.67 [CPh(a)], 127.53–129.26 (Ph), 33.36 (C, Ph),
133.95 [C, Ph(a)], 135.28 (C, Ph), 135.64 [C, Ph(a)], 158.28 (CO), 58.76
[CO(a)], 58.81 [CO(a)], 58.89 (CO), 71.44 (COO), 71.74 [COO(a)].
4b: yield 91%, mp 263–265 °C (MeOH), [a]D20 +118 (c 2.0, MeOH).
1H NMR ([2H6]DMSO) d: 0.90–1.03 (m, 3H, CMe), 1.97–2.17 (m, 1H,
CH2), 2.24–2.43 (m, 1H, CH2), 2.55 (s, 3H, NMe), 2.73 (s, 3H, NMe),
3.27–3.32 (m, 1H, CH), 3.61 (s, 3H, OMe), 6.80–7.17 (m, 10H, Ph),
8.40 (s, 1H, NH). 13C{1H} NMR ([2H6]DMSO) d: 13.19 (Me), 26.10
(NMe), 26.52 (NMe), 28.81 (CH2), 52.10 (OMe), 57.51 (CH), 82.95 (CPh),
87.63 (CPh), 127.40–128.49 (Ph), 133.76 (C, Ph), 135.41 (C, Ph), 158.64
(CO), 158.92 (CO), 172.48 (COO).
Under conditions of the synthesis (2 mol of HCl),2 the
reactions of N-carbamoyl- -amino acids 1a–e and DHI 2a,b
result in corresponding hydantoins 5a–f, which are formed as
by-products due to a pinacoline-type rearrangement of DHI 2a,b10
and the cyclization of 1a–e.11 The reactions of N-carbamoyl-
-amino acids 1d,e with DHI 2a and (S)-N-carbamoylnorvaline
1c with DHI 2b under similar conditions result in hydantoins
5d,e and 5c, respectively.
4c/4'c (3:1): yield 16%, mp 240–242 °C (MeOH). 1H NMR ([2H6]DMSO)
d: 0.93–1.05 (m, 7H, CHMe2), 2.60 (s, 3H, NMe), 2.75 (s, 3H, NMe),
2.87 (s, 3H, NMe), 2.89 (s, 3H, NMe), 3.20 (d, 1H, CH, J 9 Hz), 3.30 (d,
1H, CH, J 9 Hz), 3.44 (s, 3H, OMe), 3.51 (s, 3H, OMe), 6.77–7.25 (m,
10H, Ph), 8.37 (s, 1H, NH), 8.52 (s, 1H, NH). 13C{1H} NMR
([2H6]DMSO) d: 19.38 [CMe(a)], 19.58 (CMe), 20.06 [CMe(a)], 21.10
(CMe), 25.87 [CH(a)], 26.15 (CH), 28.43 [NMe(a)], 28.83 (NMe), 29.34
[NMe(a)], 29.79 (NMe), 51.40 [OMe(a)], 51.62 (OMe), 61.95 (CH),
83.39 (CPh), 83.50 [CPh(a)], 87.59 (CPh), 88.58 [CPh(a)], 127.36–128.44
(Ph), 133.09 [C, Ph(a)], 133.40 (C, Ph), 134.53 (C, Ph), 134.19 [C, Ph(a)],
157.86 [CO(a)], 158.51 (CO), 158.68 [CO(a)], 159.16 (CO), 170.75 (COO),
171.43 [COO(a)].
4d/4'd
(2:1): yield 74%, mp 175–177 °C (MeOH). 1H NMR ([2H6]DMSO)
d: 2.55 (s, 3H, NMe), 2.57 (s, 3H, NMe), 2.58 (s, 3H, NMe), 2.61 (s,
3H, NMe), 2.64–2.70 (m, 2H, CH2), 3.58 (s, 3H, OMe), 3.65 (s, 3H,
OMe), 6.98–7.33 (m, 15H, Ph), 8.53 (s, 1H, NH), 8.62 (s, 1H, NH).
13C{1H} NMR ([2H6]DMSO) d: 25.41 (NMe), 26.55 [NMe(a)], 29.00
(NMe), 29.16 [NMe(a)], 35.98 (CH2), 36.42 [CH2(a)], 52.13 (CH), 55.61
[CH(a)], 58.63 (OMe), 62.06 [OMe(a)], 82.70 [CPh(a)], 82.89 (CPh),
87.49 (CPh), 87.62 [CPh(a)], 126.21–129.75 (Ph), 132.62 [C, Ph(a)],
132.93 (C, Ph), 135.02 [C, Ph(a)], 135.27 (C, Ph), 138.20 [C, Ph(a)],
138.64 (C, Ph), 158.36 (CO), 158.48 [CO(a)], 158.70 [CO(a)], 158.78
(CO), 170.64 (COO), 171.05 [COO(a)].
– 97 –

Mendeleev Commun., 2008, 18, 96–98
2
3
M. D. Mashkovskii, Lekarstvennye sredstva (Drugs), Novaya Volna,
Moscow, 2005, vol. 1, p. 86 (in Russian).
Yu. B. Vikharev, L. V. Anikina, I. E. Chikunov, A. S. Sigachev, A. N.
Kravchenko, Yu. V. Shklyaev and N. N. Makhova, Vopr. Biol. Med.
Farm. Khim., 2006, no. 2, 12 (in Russian).
A. A. Bakibaev, R. R. Akmedzhanov, A. Yu. Yagovkin, T. P. Novozheeva,
V. D. Filimonov and A. S. Saratnikov, Khim. Farm. Zh., 1993, 27 (6), 29
(Pharm. Chem. J., 1993, 27 401).
(a) A. M. Rouhi, Chem. Eng. News, 2003, 81 (18), 56; (b) G. Blaschke,
H. P. Kraft, K. Fichentscher and F. Kohler, Arzneim.-Forsch., 1979, 29,
1640.
A. N. Kravchenko, K. Yu. Chegaev, I. E. Chikunov, P. A. Belyakov,
E. Yu. Maksareva, K. A. Lyssenko, O. V. Lebedev and N. N. Makhova,
Mendeleev Commun., 2003, 269.
I. E. Chikunov, A. N. Kravchenko, P. A. Belyakov, K. A. Lyssenko,
V. V. Baranov, O. V. Lebedev and N. N. Makhova, Mendeleev Commun.,
2004, 253.
These results suggest that the yields and diastereoselectivity
or diastereospecificity in the syntheses of glycolurils 3, 4 are
affected by both the amount of HCl added to the reaction mixture
and the structures of starting DHIs 2a,b and N-carbamoyl-
-amino acids 1a–e. Increasing the amount of the acid increases
the diastereoselectivity but decreases the yields of target
glycolurils 3, 4 due to an increase in the yields of hydantoins
5a–f. With DHI 2a, the yields of diastereomers 3a + 3'a and
3b + 3'b are 25% and 37%, respectively, whereas the yield of
compound 3c in the reaction with N-carbamoylnorvaline 1c
amounts to 8–10%. In the case of DHI 2b, the yields of glycolurils
4a + 4'a, 4b and 4d + 4'd are mainly in the range 74–91%; it is
only in the case of N-carbamoylvaline 1d that the yields of
compounds 4c + 4'c decrease to 10–16%. We failed to separate
the mixtures of diastereomers 3a and 3'a, 3b and 3'b, 4a and
4'a, 4c and 4'c, 4d and 4'd by crystallisation from H2O, MeOH,
PriOH or their mixtures because of similar physicochemical
properties of these compounds.
Thus, this study revealed that the -ureidoalkylation of
N-carbamoyl- -amino acids 1a–e using DHIs 2a,b, both
N-substituted and incorporating phenyl substituents at C(4)
and C(5), as the ureidoalkylating agents can occur diastereo-
selectively, and also diastereospecifically in some cases. This
allowed us to obtain the first representatives of enantiomerically
pure glycolurils (3c and 4b) and diastereomeric N- -carboxy-
alkylglucolurils with the predomination of one of the compounds
(3a and 3'a, 3b and 3'b, 4a and 4'a, 4c and 4'c, 4d and 4'd)
and to reveal the dependence of their yields on the amount of
HCl and on the structure of the DHIs and N-carbamoyl- -amino
acids 1a–e.
4
5
6
7
8
9
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12 J. Taillades, L. Boiteau, I. Beuzelin, O. Lagrille, J.-P. Biron, W. Vayaboury,
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13 A. G. Pechenkin, A. V. Evseeva, A. P. Gilev and T. V. Mikhailova, Izv.
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– 98 –