A novel multicomponent synthesis of polyfunctionalized bicyclic tetrahydropyrimidinone derivatives via mercaptoacetylative ring transformations

Article abstract of DOI:10.1016/j.carres.2009.06.017

A novel K-10 clay (nanoclay)-catalyzed expeditious synthesis of polyfunctionalized bicyclic pyrimidines using unprotected aldoses, 2-methyl-2-phenyl-1,3-oxathiolan-5-one and amidines/guanidine is reported. These polyfunctionalized bicyclic pyrimidines wer

Full text of DOI:10.1016/j.carres.2009.06.017

Carbohydrate Research 344 (2009) 2329–2335
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
A novel multicomponent synthesis of polyfunctionalized bicyclic
tetrahydropyrimidinone derivatives via mercaptoacetylative ring
transformations
*
Lal Dhar S. Yadav , Ankita Rai
Green Synthesis Lab, Department of Chemistry, University of Allahabad, Allahabad 211 002, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 May 2009
Received in revised form 2 June 2009
Accepted 17 June 2009
Available online 21 June 2009
A novel K-10 clay (nanoclay)-catalyzed expeditious synthesis of polyfunctionalized bicyclic pyrimidines
using unprotected aldoses, 2-methyl-2-phenyl-1,3-oxathiolan-5-one and amidines/guanidine is
reported. These polyfunctionalized bicyclic pyrimidines were obtained in excellent yields (72–93%) with
high cis diastereoselectivity (>94%) at the ring junction via tandem condensation, mercaptoacetylative
ring transformation and cyclization reactions. The process presents an excellent illustration of use of car-
bohydrates as renewable resources for the formation of pharmaceutically relevant fine chemicals
employing solvent-free microwave irradiation conditions in a one-pot procedure.
Keywords:
Carbohydrates
K-10 clay-catalyzed
Amidines
Ó 2009 Elsevier Ltd. All rights reserved.
Guanidine
Ring transformation
Pyrimidines
1. Introduction
trical and optical properties,16,17 and they can also be used as
functional materials.18–20 Thus, development of a convenient and
Many naturally occurring thiosugars are potential targets for
the carbohydrate-based therapeutics, such as Thiolactomycin, Sal-
acinol, Kotalonol, Tagetioxin and Mycothiol.1 Sugars incorporating
intracyclic sulfur atom (thiosugars) are of considerable interest. For
efficient methodology for the synthesis of thiosugar-fused bicyclic
pyrimidines is an interesting target of investigation.
Amongst the various general procedures available for the syn-
thesis of pyrimidines, the most general method is based on the
bis-nucleophile plus bis-electrophile methods21–27 or cross-cou-
pling reactions28,29 and is restricted to methods involving Pinner
synthesis via 3,4- and 1,6- (I);21–27 1,2- and 2,3- (II);30 1,2- and
3,4- (III);31 4,5- and 1,6- (IV);32 2,3- and 4,5- (V)33–35 and 3,4-
and 4,5- (VI)36 bond-forming original reactions (Scheme 1).
Recently, we have disclosed a synthesis of pyrimidine via novel
1,2- and 1,6- bond-forming reactions (VII, Scheme 1).37 Lewis
acid-promoted multicomponent organic transformations are
gaining increasing popularity due to their economic and ecological
efficacy. Also, in situations where a premium is put on speed,
diversity and efficiency, multicomponent reactions (MCRs) are of
example, 5-thio-D-glucose (Fig. 1) is an a
-glycosidase inhibitor,2
and some 5-thioglycosidases have antithrombotic effect3 and other
useful medicinal properties.1 The biological interest in thiosugars
has expanded the studies on diabetes enzyme inhibitor, antiviral
and antitumour activities.4–9
Pyrimidines are found widely as a core structure in a large vari-
ety of compounds that exhibit important biological activities.10–12
Pyrimidines and their derivatives as a class of extremely important
heterocyclic compounds are used in a wide array of synthetic and
industrial applications. They not only are an integral part of the ge-
netic materials, namely, DNA and RNA as nucleotides and nucleo-
sides, but also play critical roles especially in pharmaceutical
fields.13,14 For example,
L-lathyrine, a naturally occurring 2-amino-
pyrimidine, shows a wide range of biological activities such as pol-
len growth inhibition and antitumour and hypoglycemic activities
(Fig. 1).15 Furthermore, some pyrimidine derivatives can give sta-
ble and good quality nanomaterials having many important elec-
NH2
HO
HO
5-thio-
S
OH
OH
N
N
CO2H
NH2
OH
-glucose
D
L
-lathyrine
* Corresponding author. Tel.: +91 5322500652; fax: +91 5322460533.
E-mail address: ldsyadav@hotmail.com (L. D. S. Yadav).
Figure 1.
0008-6215/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2009.06.017

2330
L. D. S. Yadav, A. Rai / Carbohydrate Research 344 (2009) 2329–2335
Table 1
N
C
C
Optimization of reaction conditions for compound 4a (R = Me)
C
N
N
N
C
I
N
Entry
Catalyst system
MW
Oil-bath
Timea (h) Yieldb (%)
C
C
II
N
Timea (min)
Yieldb (%)
III
4
C
N
1
2
3
4
5
6
K-10 clay
10
12
11
13
16
16
91
53
62
25
17
20
7
7
8
10
10
9
56
22
31
19
11
13
C
C
C
C
5
6
N
N
3
2
N
VIII
IV
CeCl3ꢀ7H2O
CeCl3ꢀ7H2O/NaI
Silica gel
N
N
1
Present work
C
Neutral alumina
Acidic alumina
N
C
V
VII
VI
C
a
N
C
Time for the completion of the reaction at 80 °C as indicated by TLC.
Yield of isolated and purified product 4a.
N
C
b
C
N
C
N
N
nificantly lower yield of 4a was obtained using oil-bath heating
rather than the MW-activated method with all the catalyst systems
(Table 1). After optimization of the reaction conditions, the
polyfunctionalized bicyclic pyrimidines 4 and 5 were efficiently
synthesized by microwave (MW) irradiation of an intimate sol-
Scheme 1. Various routes for pyrimidine synthesis.
increasing importance. Again, due to interest in the preparation of
5-thiosugar derivatives many 5-thiosugars were synthesized from
sugars,38–41 instead, however these methods generally require
multisteps. Thus, we have devised a novel K-10 clay (nanoclay)-
catalyzed multicomponent reaction for the annulation of the phar-
maceutically important thiosugars with a pyrimidine moiety,
which would afford attractive scaffolds for exploiting their chemi-
cal diversity. Also, the presence of free polyhydroxyl groups would
enhance water solubility and biodegradability of the target
molecules.
This article reports a conceptually new route for the synthesis of
polyfunctionalized pyrimidines via 3,4-, 4,5- and 1,6 bond-forming
reaction (VIII, Scheme 1) using a [3+1+2] coupling protocol starting
from unprotected aldoses 1, N-unsubstituted amidines/guanidine
2 and activated mercaptoacetic acid 3 (Scheme 2). The present
unprecedented synthesis of functionalized bicyclic pyrimidines 4
and 5 is an outcome of our continued interest in solvent-free het-
erocyclization strategies,42–47 especially using carbohydrates as
raw materials.48,49 Furthermore, the present synthetic protocol is
in accord with ‘renewable resources’, a new and rapidly developing
concept in environmental and chemical sciences that concerns the
wide use of biorenewable materials for industry.50
vent-free mixture of
2-methyl-2-phenyl-1,3-oxathiolone-5-one
D
-xylose/
D
-glucose 1, amidines/guanidine 2,
and the nanoclay,
3
Montmorillonite K-10 (particle size 32.7 nm), at 80 °C for 7–
12 min in a Chemical Laboratory Microwave Oven (Model: BP-
310/50, 230 V, 50 Hz power input) (Scheme 2).
Isolation and purification by recrystallization from ethanol
afforded 4 and 5 in 72–93% yields with >94% diastereoselectivity
(Table 2) in favor of the isomer with cis ring junction as deter-
mined by 1H NMR spectroscopy.47,51–55 The crude isolates were
checked by 1H NMR for their diastereomeric ratios to note any
inadvertent alteration of these ratios during subsequent purifica-
tion. In products 4 and 5, the rings are cis fused as indicated by
the coupling constants of ring junction protons 4a-H and 8a-H
(J4a,8a = 4.9 Hz). It is also supported by NOE interaction experi-
ments. For example, 11.6% and 12.3% NOEs were observed between
4a-H and 8a-H in products 4a and 5a, respectively, indicating that
4a-H and 8a-H are located on the same face of the molecule, hence
confirming the cis fusion of the rings.
The chiral carbons of the precursor carbohydrates retain their
configuration in the product if they are not involved in any bond
breaking/formation. This fact is supported by the observation that
there was no change in the absolute configuration of any chiral car-
2. Results and discussion
bon of
ture of
D
-xylose or
-xylose or
D
-glucose when an intimate solvent-free mix-
D
D
-glucose (2.0 mmol) and K-10 clay (0.20 g)
In our initial experiment we optimized the catalyst for the pres-
ent reaction. We have examined various mineral catalysts for the
formation of 4a (R = Me). Among the catalysts tested, K-10 clay
gave the best result (Table 1, entry 1). CeCl3ꢀ7H2O/NaI-system
and CeCl3ꢀ7H2O afforded the product 4a in moderate to good yields
(Table 1, entries 2 and 3), while poor yields of product 4a were ob-
tained in the case of silica gel and neutral or acidic alumina (Table
1, entries 4–6). Moreover, the reaction did not take place when ba-
sic alumina was used as the catalyst. It was also observed that sig-
was subjected to MW irradiation at 80 °C for 15 min, that is, under
the present reaction conditions. The formation of 4 and 5 may be
tentatively rationalized by intramolecular attack of the nitrogen
atom of the amidine/guanidine moiety at the carbonyl carbon (C-
5) of the 2-methyl-2-phenyl-1,3-oxathiolan-5-one 3 to yield the
target compounds 4 and 5. This conclusion is based on the obser-
vation that the representative intermediate compounds 7a and
7g have been isolated in 52% and 59% yields, respectively, and that
OH
OH
S
R
H
N
O
OH
n = 3
n = 4
H
NH
CHO
NH
4
(i) MW
K-10 clay
(ii) H3O+
S
(CHOH)n
Ph
Me
O
R
NH2
O
HO
OH
OH
CH2OH
S
H
D-xylose; n = 3
O
D-glucose; n = 4
OH
5
H
N
NH
3
2
1
R
Scheme 2. Synthesis of bicyclic pyrimidines 4 and 5.

L. D. S. Yadav, A. Rai / Carbohydrate Research 344 (2009) 2329–2335
2331
Table 2
Microwave-activated synthesis of bicyclic pyrimidines 4 and 5
Entry
D
-Glucose/
D
-xylose 1
Amidine or guanidine 2
Activated acid 3
Product 4 or 5
Yielda,b (%) (time, minc)
cis:trans ratiod
OH
OH
CHO
S
NH
S
H
Ph
O
(CHOH)3
CH2OH
O
1
4a
91 (8)
95:5
OH
O
H
H3C
NH2
Me
N
NH
CH3
OH
OH
CHO
S
NH
NH2
H
N
(CHOH)3
CH2OH
O
2
3
4
3
3
3
4b
93 (7)
87 (9)
84 (10)
96:4
95:5
96:4
OH
H
H2N
NH
NH2
OH
OH
CHO
NH
NH2
S
(CHOH)3
CH2OH
H
N
4c
O
O
H
OH
H
NH
OH
OH
CHO
S
S
H
N
NH
NH2
OH
(CHOH)3
CH2OH
4d
H
NH
OH
OH
H
N
NH2
NH2
CHO
O
O
OH
H
(CHOH)3
CH2OH
NH
5
3
4e
76 (11)
97:3
O2N
NO2
S
OH
OH
H
N
NH
NH2
CHO
OH
H
(CHOH)3
CH2OH
NH
6
3
4f
84 (11)
95:5
H2N
NH2
HO
S
OH
OH
CHO
NH
NH2
H
(CHOH)4
CH2OH
O
7
3
3
5a
86 (9)
96:4
97:3
OH
H
H3C
H2N
N
NH
CH3
HO
OH
OH
CHO
S
NH
NH2
H
(CHOH)4
CH2OH
O
8
5b
89 (8)
OH
H
N
NH
NH2
(continued on next page)

2332
L. D. S. Yadav, A. Rai / Carbohydrate Research 344 (2009) 2329–2335
Table 2 (continued)
Entry
D-Glucose/D-xylose 1
Amidine or guanidine 2
Activated acid 3
Product 4 or 5
Yielda,b (%) (time, minc)
cis:trans ratiod
HO
CHO
OH
OH
NH
S
(CHOH)4
CH2OH
9
3
5c
85 (11)
95:5
H
O
H
NH2
OH
H
N
NH
HO
OH
OH
CHO
S
NH
H
O
(CHOH)4
CH2OH
OH
10
3
3
3
5d
82 (11)
72 (12)
81 (12)
97:3
97:3
96:4
H
NH
NH2
N
HO
OH
OH
S
H
NH
NH2
CHO
O
OH
H
(CHOH)4
CH2OH
N
NH
11
5e
O2N
NO2
HO
OH
OH
S
H
NH
NH2
CHO
O
OH
H
NH
(CHOH)4
CH2OH
12
5f
N
H2N
NH
a
Microwave irradiation time at 80 °C.
Yield of isolated and purified products.
b
c
All compounds gave C, H and N analyses within 0.34% and satisfactory spectral (IR, 1H NMR, 13C NMR and FAB MS) data.
As determined by 1H NMR spectroscopy of the crude products.
d
these could be converted to the corresponding bicyclic products 4a
and 5a in quantitative yield. Furthermore, the acetophenone,
which was used to activate the mercaptoacetic acid to act as a
masked mercapto acid, was removed during the course of reaction
without requiring any protection–deprotection step yielding com-
pounds 4 and 5 (Scheme 3).
In conclusion, we have developed a one-pot expeditious synthe-
sis of polyfunctionalized bicyclic pyrimidines using unprotected
aldoses, 2-methyl-2-phenyl-1,3-oxathiolan-5-one and amidines/
guanidine. The reaction is nanoclay-catalyzed and effected under
solvent-free MW irradiation conditions to afford thiosugar-fused
bicyclic pyrimidine scaffolds with high cis diastereoselectivity at
the ring junction. The process represents an excellent illustration
of use of carbohydrates as renewable resources for the formation
of pharmaceutically relevant fine chemicals.
as internal reference. Mass (EI) spectra were recorded on a JEOL D-
300 mass spectrometer. Elemental analyses were carried out in a
Coleman automatic carbon, hydrogen and nitrogen analyzer. A
Chemical Laboratory Microwave Oven (Model; BP-310/50, 230 V,
50 Hz power input) was used for all experiments. All chemicals
used were of reagent grade and were used as received without fur-
ther purification. Silica gel-G was used for TLC.
3.2. 2-Substituted-(4aR,7S,8R,8aS)-7,8-dihydroxy-6-(hydroxy-
methyl)-6,7,8,8a-tetrahydro-1H-thiopyrano[3,2-d]pyrimidin-
4(4aH)-ones: (4) and 2-substituted-(4aR,7S,8R,8aS)-6-((R)-1,2-
dihydroxyethyl)-7,8-dihydroxy-6,7,8,8a-tetrahydro-1H-
thiopyrano[3,2-d]pyrimidin-4(4aH)-ones: (5); General
procedure
An intimate solvent-free mixture of aldose 1 (2.0 mmol), ami-
dines/guanidine 2 (2.0 mmol), 1,3-oxathiolan-5-one 3 (2.0 mmol)
and Montmorillonite K-10 clay (0.20 g, particle size 32.7 nm) was
taken in a 20-mL vial and subjected to MW irradiation at 80 °C
for 7–12 min (Table 1). After completion of the reaction as indi-
cated by TLC hexane/AcOEt, 7:3, v/v), water (10 mL) was added
to the reaction mixture with continuous stirring. The yellowish
precipitate thus obtained was washed with water to give the crude
product which was recrystallized from ethanol to afford a diaste-
reomeric mixture (>97:<3); in the crude products the ratio was
>94:6, as determined by 1H NMR spectroscopy. The product on sec-
3. Experimental
3.1. General
Melting points were determined by open glass capillary method
and are uncorrected. IR spectra in KBr were recorded on a Perkin–
Elmer 993 IR spectrophotometer. 1H NMR spectra were recorded
on a Bruker WM-40 C (400 MHz) FT spectrometer in DMSO-d6
using TMS as internal reference. 13C NMR spectra were recorded
on the same instrument at 100 MHz in DMSO-d6 and TMS was used

L. D. S. Yadav, A. Rai / Carbohydrate Research 344 (2009) 2329–2335
2333
3.2.3. Compound 4c
CH2OH
O
H
Pale yellow powder; mp 109–113 °C. IR (KBr):
m
= 3345, 3324,
C
NH
NH2
MW
K-10
clay
(CHOH)n
1686, 1673, 1149, 690 cmꢁ1
.
1H NMR (400 MHz; DMSO-
(CHOH)n
S
Ph
Me
R
O
0
N
d6 + D2O): d = 1.1 (s, 1H, CH), 3.34 (ddd, 1H, J6,7 = 9.7 Hz, J1 Ha,
6
O
3
CH2OH
0
0
0
2
= 5.9 Hz, J1 Hb, 6 = 2.5 Hz, 6-H), 3.48 (dd, 1H, J1 Ha, 1 Hb = 12.0,
6
1 n = 3, 4
CH2OH
J1 Ha,6 = 5.9 Hz, 10-Ha), 3.74 (dd, 1H, J6,7 = 9.7 Hz, J7,8 = 9.1 Hz, 7-H),
HN
R
0
3.93 (dd, 1H, J1 Ha, 1 Hb = 12.0 Hz, J1 Hb,6 = 2.5 Hz, 10-Hb), 4.06 (dd,
1H, J7,8 = 9.1 Hz, J8,8a = 7.2 Hz, 8-H), 5.06 (dd, 1H, J8,8a = 7.2 Hz,
J4a,8a = 4.6 Hz, 8a-H), 6.18 (d, 1H, J4a,8a = 4.6 Hz, 4a-H). 13C NMR
(DMSO-d6): d = 42.9, 44.8, 47.6, 60.9, 74.6, 77.5, 164, 204. (FAB)
m/z = 233 [MH+]. Anal. Calcd for C8H12N2O4S: C, 41.37; H, 5.21; N,
12.06. Found: C, 41.03; H, 5.48; N, 12.21.
0
0
0
CH2OH
(CHOH)n
H
SH
(CHOH)n
H
O
- PhCOMe
H
NH
H
R
S
N
NH
Ph
Me
NH
O
O
7
R
8
OH
3.2.4. Compound 4d
OH
1'
HO
H
OH
6
5
Pale yellow powder; mp 124–127 °C. IR (KBr):
m = 3342, 3326,
OH
7
S
3047, 1689, 1671, 1601, 1505, 1451, 1143, 686 cmꢁ1
.
1H NMR
SH
H
8
8a
4a
O
O
0
OH
(400 MHz; DMSO-d6 + D2O): d = 3.31 (ddd, 1H, J6,7 = 9.4 Hz, J1 Ha, 6
OH
-H2O
4
H
2 NH
H
NH
N
0
0
0
N
= 6.2 Hz, J1 Hb, 6 = 2.6 Hz, 6-H), 3.49 (dd, 1H, J1 Ha, 1 Hb = 12.3,
3
1
J1 Ha,6 = 6.2 Hz, 10-Ha), 3.71 (dd, 1H, J6,7 = 9.4 Hz, J7,8 = 9.1 Hz, 7-H),
0
R
R
4
3.91 (dd, 1H, J1 Ha, 1 Hb = 12.3 Hz, J1 Hb,6 = 2.6 Hz, 10-Hb), 4.08 (dd,
1H, J7,8 = 9.1 Hz, J8,8a = 7.4 Hz, 8-H), 5.04 (dd, 1H, J8,8a = 7.4 Hz,
J4a,8a = 4.7 Hz, 8a-H), 6.14 (d, 1H, J4a,8a = 4.7 Hz, 4a-H), 7.07–7.80
(m, 5H ArH). 13C NMR (DMSO-d6): d = 40.5, 45.4, 47.9, 61.5, 74.5,
76.8, 125.7, 128.7, 129.9, 132.1, 165, 204. (FAB) m/z = 309 [MH+].
Anal. Calcd for C14H16N2O4S: C, 54.53; H, 5.23; N, 9.08. Found: C,
54.84; H, 5.04; N, 9.30.
8
, n = 3
0
0
0
HO
2'
7
OH
HO 1'
OH
OH
HO
OH
6
H 5S
SH
-H2O
H
8OH
O
8a
O
OH
4a
4
H
N
NH
H
N
NH
1
3
2
R
3.2.5. Compound 4e
5
R
8,
n = 4
Pale yellow powder; 128–131 °C. IR (KBr):
m = 3345, 3325, 3050,
1684, 1679, 1603, 1510, 1451, 1143, 691 cmꢁ1. 1H NMR (400 MHz;
Scheme 3. Plausible mechanism for the formation of bicyclic pyrimidines 4 and 5.
0
DMSO-d6 + D2O): d = 3.31 (ddd, 1H, J6,7 = 9.6 Hz, J1 Ha, 6 = 6.1 Hz,
0
0
0
0
J1 Hb, 6 = 2.7 Hz, 6-H), 3.49 (dd, 1H, J1 Ha, 1 Hb = 12.4, J1 Ha,6 = 6.1 Hz,
1’-Ha), 3.71 (dd, 1H, J6,7 = 9.6 Hz, J7,8 = 9.2 Hz, 7-H), 3.92 (dd, 1H,
J1 Ha, 1 Hb = 12.4 Hz, J1 Hb,6 = 2.7 Hz, 10-Hb), 4.09 (dd, 1H,
J7,8 = 9.2 Hz, J8,8a = 7.5 Hz, 8-H), 5.07 (dd, 1H, J8,8a = 7.5 Hz,
J4a,8a = 4.4 Hz, 8a-H), 6.16 (d, 1H, J4a,8a = 4.4 Hz, 4a-H), 7.76 (d, 2H,
J = 8.3 Hz, ArH), 8.32 (d, 2H, J = 8.3 Hz, ArH). 13C NMR (DMSO-d6):
d = 40.7, 45.9, 47.8, 60.7, 74.9, 77.2, 120.9, 127.3, 135.9, 149.4,
163, 202. (FAB) m/z = 354 [MH+]. Anal. Calcd for C14H15N3O6S: C,
47.59; H, 4.28; N, 11.89. Found: C, 47.33; H, 4.58; N, 12.14.
0
0
0
ond recrystallization from ethanol furnished an analytically pure
sample of a single diastereomer 4 or 5 (Table 1). On the basis of
the comparison of J values with literature values,47,51–55 the cis ste-
reochemistry was assigned to 4 and 5 at the ring junction as the
coupling constant (J4a,8a = 4.9 Hz) of the major cis diastereomer
was lower than that of the minor trans diastereomer
(J4a,8a = 10.1 Hz).
3.2.1. Compound 4a
3.2.6. Compound 4f
Pale yellow powder; mp 117–120 °C. IR (KBr):
m
= 3341, 3325,
Pale yellow powder; mp 121–123 °C. IR (KBr):
m = 3347, 3325,
1685, 1671, 1145, 692 cmꢁ1
.
1H NMR (400 MHz; DMSO-
1687, 1677, 1148, 686 cmꢁ1 1H NMR (400 MHz; DMSO-
.
0
0
0
d6 + D2O): d = 1.2 (s, 3H, CH3), 3.33 (ddd, 1H, J6,7 = 9.5 Hz, J1 Ha,
d6 + D2O): d = 3.31 (ddd, 1H, J6,7 = 9.4 Hz, J1 Ha, 6 = 6.2 Hz, J1 Hb,
6
6
= 2.6 Hz, 6-H), 3.49 (dd, 1H, J1 Ha, 1 Hb = 12.2, J1 Ha,6 = 6.2 Hz, 10-
Ha), 3.71 (dd, 1H, J6,7 = 9.4 Hz, J7,8 = 9.3 Hz, 7-H), 3.92 (dd, 1H,
0
0
0
0
0
0
= 6.2 Hz, J1
6 = 2.5 Hz, 6-H), 3.49 (dd, 1H, J1 Ha, 1 Hb = 12.1,
Hb,
J1 Ha,6 = 6.2 Hz, 10-Ha), 3.70 (dd, 1H, J6,7 = 9.5 Hz, J7,8 = 9.3 Hz, 7-H),
0
3.89 (dd, 1H, J1 Ha, 1 Hb = 12.1 Hz, J1 Hb,6 = 2.4 Hz, 10-Hb), 4.09 (dd,
1H, J7,8 = 9.2 Hz, J8,8a = 7.3 Hz, 8-H), 5.05 (dd, 1H, J8,8a = 7.3 Hz,
J4a,8a = 4.9 Hz, 8a-H), 6.17 (d, 1H, J4a,8a = 4.9 Hz, 4a-H). 13C NMR
(DMSO-d6): d = 25.7, 41.2, 45.3, 48.7, 61.9, 73.8, 77.5, 165, 203.
(FAB): m/z = 247 [MH+]. Anal. Calcd for C9H14N2O4S: C, 43.89; H,
5.73; N, 11.37. Found: C, 43.58; H, 5.50; N, 11.66.
J1 Ha, 1 Hb = 12.2 Hz, J1 Hb,6 = 2.6 Hz, 10-Hb), 4.09 (dd, 1H,
J7,8 = 9.3 Hz, J8,8a = 7.1 Hz, 8-H), 5.03 (dd, 1H, J8,8a = 7.1 Hz,
J4a,8a = 4.9 Hz, 8a-H), 6.18 (d, 1H, J4a,8a = 4.9 Hz, 4a-H), 6.49–7.10
(m, 4H ArH). 13C NMR (DMSO-d6): d = 38.5, 41.2, 44.6, 62.6, 67.9,
73.4, 116.7, 123.3, 127.1, 148.4, 163.2, 201. (FAB) m/z = 324
[MH+]. Anal. Calcd for C14H17N3O4S: C, 52.00; H, 5.30; N, 12.99.
Found: C, 52.21; H, 5.42; N, 13.32.
0
0
0
0
0
0
3.2.2. Compound 4b
Pale yellow powder; mp 114–116 °C. IR (KBr):
m
= 3343, 3321,
3.2.7. Compound 5a
1687, 1675, 1147, 689 cmꢁ1 1H NMR (400 MHz; DMSO-
.
Pale yellow powder; mp 123–126 °C. IR (KBr):
1689, 1672, 1145, 689 cmꢁ1 1H NMR (400 MHz; DMSO-d6 + D2O):
d = 1.4 (s, 3H, CH3), 3.27 (ddd, 1H, J1 6 = 6.0 Hz, J1 2 Ha = 5.6 Hz,
m = 3343, 3329,
0
0
d6 + D2O): d = 3.34 (ddd, 1H, J6,7 = 9.6 Hz, J1 Ha, 6 = 5.9 Hz, J1 Hb,
.
6
= 2.7 Hz, 6-H), 3.45 (dd, 1H, J1 Ha, 1 Hb = 12.0, J1 Ha,6 = 5.9 Hz, 10-
0
0
0
0
0
0
J1 2 Hb = 2.6 Hz, 10H), 3.44 (ddd, 1H, J6,7 = 9.0 Hz, J1 Ha, 6 = 6.0 Hz, 6-
0
0
0
Ha), 3.75 (dd, 1H, J6,7 = 9.6 Hz, J7,8 = 8.9 Hz, 7-H), 3.93 (dd, 1H,
J1 Ha, 1 Hb = 12.0 Hz, J1 Hb,6 = 2.7 Hz, 10-Hb), 4.09 (dd, 1H,
J7,8 = 8.9 Hz, J8,8a = 7.4 Hz, 8-H), 5.04 (dd, 1H, J8,8a = 7.4 Hz,
J4a,8a = 4.7 Hz, 8a-H), 6.17 (d, 1H, J4a,8a = 4.7 Hz, 4a-H).). 13C NMR
(DMSO-d6): d = 37.4, 45.7, 48.9, 61.2, 74.7, 77.3, 162, 202. (FAB):
m/z = 248 [MH+]. Anal. Calcd for C8H13N3O4S: C, 38.86; H, 5.30; N,
16.99. Found: C, 39.06; H, 4.97; N, 16.67.
H), 3.59 (dd, 1H, J1 Ha, 1 Hb = 11.7, J1 Ha,6 = 5.6 Hz, 20-Ha), 3.75 (dd,
0
0
0
0
0
0
0
0
1H, J6,7 = 9.4 Hz, J7,8 = 9.0 Hz, 7-H), 3.91 (dd, 1H, J1 Ha, 1 Hb = 11.7 Hz,
J1 Hb,6 = 2.6 Hz, 20-Hb), 4.23 (dd, 1H, J7,8 = 9.4 Hz, J8,8a = 7.1 Hz, 8-H),
0
4.99 (dd, 1H, J8,8a = 7.1 Hz, J4a,8a = 4.7 Hz, 8a-H), 6.20 (d, 1H,
J4a,8a = 4.7 Hz, 4a-H). 13C NMR (DMSO-d6): d = 25.6, 36.9, 40.5, 44.8,
67.3, 72.4, 73.9, 77.6, 164.2, 201.4. (FAB) m/z = 277 [MH+]. Anal.

2334
L. D. S. Yadav, A. Rai / Carbohydrate Research 344 (2009) 2329–2335
0
0
0
Calcd for C10H16N2O5S: C, 43.47; H, 5.84; N, 10.14. Found:C, 43.14; H,
6.08; N, 9.98.
J7,8 = 9.3 Hz, 7-H), 3.91 (dd, 1H, J1 Ha, 1 Hb = 11.9 Hz, J1 Hb,6 = 2.6 Hz,
20-Hb), 4.23 (dd, 1H, J7,8 = 9.8 Hz, J8,8a = 7.0 Hz, 8-H), 4.98 (dd, 1H,
J8,8a = 7.0 Hz, J4a,8a = 4.7 Hz, 8a-H), 6.23 (d, 1H, J4a,8a = 4.7 Hz, 4a-H),
6.52–7.14 (m, 4H ArH). 13C NMR (DMSO-d6): d = 35.7, 40.6, 45.8,
66.0, 67.9, 73.1, 74.5, 116.1, 121.4, 126.8, 149.2, 163.7, 200.9. (FAB)
m/z = 354 [MH+]. Anal. Calcd for C15H19N3O5S: C, 50.98; H, 5.42; N,
11.89. Found: C, 51.20; H, 5.18; N, 11.70.
3.2.8. Compound 5b
Pale yellow powder; mp 119–121 °C. IR (KBr):
1685, 1671, 1145, 692 cmꢁ1 1H NMR (400 MHz; DMSO-
d6 + D2O): d = 3.25 (ddd, 1H, J1 6 = 6.1 Hz, J1 2 Ha = 5.7 Hz,
m = 3341, 3325,
.
0
0
0
J1 2 Hb = 2.3 Hz, 10H), 3.39 (ddd, 1H, J6,7 = 8.9 Hz, J1 Ha, 6 = 6.1 Hz, 6-
0
0
0
H), 3.61 (dd, 1H, J1 Ha, 1 Hb = 12.0, J1 Ha,6 = 5.7 Hz, 20-Ha), 3.76 (dd,
3.3. Isolation of Michael adducts 7a (n = 3, R = Me) and 7g (n = 4,
R = Me) and their conversion into the corresponding bicyclic
products 4a and 5a; General procedure
0
0
0
0
0
1H, J6,7 = 9.3 Hz, J7,8 = 8.9 Hz, 7-H), 3.91 (dd, 1H, J1 Ha, 1 Hb = 12.0 Hz,
J
= 2.3 Hz, 20-Hb), 4.20 (dd, 1H, J7,8 = 9.3 Hz, J8,8a = 7.5 Hz, 8-H),
10 Hb,6
4.95 (dd, 1H, J8,8a = 7.5 Hz, J4a,8a = 5.0 Hz, 8a-H), 6.27 (d, 1H,
J4a,8a = 5.0 Hz, 4a-H). 13C NMR (DMSO-d6): d = 36.5, 37.8, 45.6,
67.9, 72.1, 73.3, 77.5, 163, 201.9. (FAB) m/z = 278 [MH+]. Anal.
Calcd for C9H15N3O5S: C, 38.98; H, 5.45; N, 15.15. Found: C,
39.25; H, 5.76; N, 14.84.
The procedure followed was the same as that described above
for the synthesis of 4 and 5 except that the duration of MW irradi-
ation in this case was 4–5 min instead of 7–12 min for 4 and 5. The
adducts 7a and 7g were recrystallized from ethanol to give a dia-
stereomeric mixture (>97:<3; in the crude products the ratio was
>94:<6, as determined by 1H NMR spectroscopy) which was again
recrystallized from ethanol to obtain an analytical sample of 7a
and 7g. The adducts 7a and 7g were assigned the syn stereochem-
istry as their 1H NMR spectra exhibited a lower coupling constant
JNCH, SCH = 4.5 Hz than that of the minor (<4%) diastereomer (anti),
JNCH, SCH = 9.8 Hz.47,51–55 Finely powdered intermediate compounds
7a and 7g were MW irradiated for 4–6 min in the same way as de-
scribed above for the synthesis of 4 and 5 to give the corresponding
bicyclic products 4 and 5, quantitatively.
3.2.9. Compound 5c
Pale yellow powder; mp 117–119 °C. IR (KBr):
m = 3341, 3325,
1685, 1671, 1145, 692 cmꢁ1
.
1H NMR (400 MHz; DMSO-
0
d6 + D2O): d = 0.9 (s, 1H, CH), 3.25 (ddd, 1H, J1 6 = 6.3 Hz,
J1 2 Ha = 5.9 Hz, J1 2 Hb = 2.7 Hz, 10H), 3.42 (ddd, 1H, J6,7 = 9.3 Hz,
0
0
0
0
0
0
0
0
J1 Ha, 6 = 6.3 Hz, 6-H), 3.58 (dd, 1H, J1 Ha, 1 Hb = 11.8, J1 Ha,6 = 5.9 Hz,
20-Ha), 3.77 (dd, 1H, J6,7 = 9.5 Hz, J7,8 = 9.3 Hz, 7-H), 3.87 (dd, 1H,
J1 Ha, 1 Hb = 11.8 Hz, J1 Hb,6 = 2.7 Hz, 20-Hb), 4.24 (dd, 1H,
J7,8 = 9.5 Hz, J8,8a = 7.2 Hz, 8-H), 4.97 (dd, 1H, J8,8a = 7.2 Hz,
J4a,8a = 4.9 Hz, 8a-H), 6.21 (d, 1H, J4a,8a = 4.9 Hz, 4a-H). 13C NMR
(DMSO-d6): d = 35.8, 42.5, 45.9, 66.7, 71.3, 72.7, 76.8, 162.9,
200.7. (FAB) m/z = 263 [MH+]. Anal. Calcd for C9H14N2O5S: C,
41.21; H, 5.38; N, 10.68. Found: C, 41.50; H, 5.16; N, 10.87.
0
0
0
3.3.1. Compound 7a (n = 3, R = Me)
Pale yellow powder; mp 109–110 °C. IR (KBr):
1776, 1679, 1602, 1582, 1451 cmꢁ1 1H NMR (400 MHz; DMSO-
d6 + D2O): d = 1.0 (s, 3H, Me), 4.04 (dd, 1H, J1 ,2 = 6.9 Hz,
m = 3349, 3008,
.
0
0
J1 NCH = 5.5 Hz, 10-H), 4.15 (dd, 1H, J4 Ha,Hb = 10.4 Hz, J4 Hb,3 = 5.2 Hz,
0
0
0
0
3.2.10. Compound 5d
40-Hb), 4.41 (dd, 1H, J1 ,2 = 6.9 Hz, J2’,3’ = 4.5 Hz, 20-H), 4.64 (ddd,
0
0
Pale yellow powder; mp 117–119 °C. IR (KBr):
m
= 3341, 3325,
1685, 1671, 1145, 692 cmꢁ1
.
1H NMR (400 MHz; DMSO-d6 + D2O):
1H, J3,4 Hb = 5.2 Hz, J3,4 Ha = 5.2 Hz, 30-H), 4.87 (dd, 1H, J4 Ha,Hb
=
0
0
0
d = 3.25 (ddd, 1H, J1 6 = 6.3 Hz, J1 2 Ha = 5.9 Hz, J1 2 Hb = 2.7 Hz, 10H),
10.4 Hz, J3,4 Ha = 7.1 Hz, 4’-Ha), 5.04 (dd, 1H, J1 ,NCH = 5.5 Hz,
JSCH,NCH = 4.5 Hz, NCH), 6.71 (d, 1H, JSCH,NCH = 4.5 Hz, SCH), 7.07–
7.64 (m, 5H arom.). 13C NMR (DMSO-d6): d = 21.4, 28.5, 47.6,
49.2, 64.8, 71.9, 73.1, 74.7, 96.2, 126.7, 128.2, 129.4, 138.3, 165.0,
174.0. (FAB) m/z = 385 [MH+]. Anal. Calcd for C17H24N2O6S: C,
53.11 H, 6.29; N, 7.29. Found: C, 53.42; H, 6.58; N, 7.08.
0
0
0
0
0
0
0
0
0
3.42 (ddd, 1H, J6,7 = 9.3 Hz, J1 Ha, 6 = 6.3 Hz, 6-H), 3.58 (dd, 1H, J1 Ha,
1 Hb = 11.8, J1 Ha,6 = 5.9 Hz, 20-Ha), 3.77 (dd, 1H, J6,7 = 9.5 Hz,
0
0
0
0
0
J7,8 = 9.3 Hz, 7-H), 3.87 (dd, 1H, J1 Ha, 1 Hb = 11.8 Hz, J1 Hb,6 = 2.7 Hz,
20-Hb), 4.24 (dd, 1H, J7,8 = 9.5 Hz, J8,8a = 7.2 Hz, 8-H), 4.97 (dd, 1H,
J8,8a = 7.2 Hz, J4a,8a = 4.9 Hz, 8a-H), 6.21 (d, 1H, J4a,8a = 4.9 Hz, 4a-H),
7.08–7.84 (m, 5H ArH). 13C NMR (DMSO-d6): d = 35.8, 42.5, 45.9,
66.7, 71.3, 72.7, 76.8, 125.8, 128.7, 129.8, 132.2 162.9, 200.7. (FAB)
m/z = 263 [MH+]. Anal. Calcd for C9H14N2O5S: C, 41.21; H, 5.38; N,
10.68. Found: C, 41.50; H, 5.16; N, 10.87.
3.3.2. Compound 7g (n = 4, R = Me)
Pale yellow powder; mp 123–125 °C. IR (KBr):
1783, 1596, 1578, 1445, 1095 cmꢁ1 1H NMR (400 MHz; DMSO-
d6 + D2O): d = 1.3 (s, 3H, Me), 4.09 (dd, 1H, J1 ,2 = 6.4 Hz,
m = 3147, 3012,
.
0
0
J1 NCH = 5.2 Hz, 10-H), 4.17 (dd, 1H, J4 Ha,Hb = 10.2 Hz, J4 Hb,3 = 5.7 Hz,
0
0
0
0
3.2.11. Compound 5e
40-Hb), 4.37 (dd, 1H, J1 ,2 = 6.4 Hz, J2 ,3 = 4.6 Hz, 2-H), 4.60 (ddd, 1H,
0
0
0
0
Pale yellow powder; mp 135–137 °C. IR (KBr):
1685, 1671, 1145, 692 cmꢁ1 1H NMR (400 MHz; DMSO-
d6 + D2O): d = 3.26 (ddd, 1H, J1 6 = 6.4 Hz, J1 2 Ha = 5.9 Hz,
m
= 3341, 3325,
J3,4 Hb = 4.6 Hz, J3,4 Ha = 4.2 Hz, 40-H), 4.87 (dd, 1H, J4 Ha,Hb = 10.2 Hz,
0
0
0
.
J3,4 Ha = 5.7 Hz, 50-Ha), 5.06 (dd, 1H, J1 ,NCH = 5.2 Hz, JSCH,NCH = 4.4 Hz,
NCH), 6.69 (d, 1H, JSCH,NCH = 4.4 Hz, SCH), 7.09–7.71 (m, 5H arom.).
13C NMR (DMSO-d6): d = 20.6, 28.8, 47.1, 48.7, 65.6, 70.9, 72.3, 73.4,
75.1, 94.8, 126.7, 128.2, 129.4, 139.1, 164.9, 173.6. (FAB) m/z = 415
[MH+]. Anal. Calcd for C18H26N2O7S: C, 52.16 H, 6.32; N, 6.76.
Found: C, 51.95; H, 6.62; N, 6.49.
0
0
0
0
0
J1 2 Hb = 2.4 Hz, 10H), 3.41 (ddd, 1H, J6,7 = 9.4 Hz, J1 Ha, 6 = 6.4 Hz,
0
0
0
6-H), 3.59 (dd, 1H, J1 Ha, 1 Hb = 11.6, J1 Ha,6 = 5.9 Hz, 20-Ha), 3.76
(dd, 1H, J6,7 = 9.7 Hz, J7,8 = 9.4 Hz, 7-H), 3.90 (dd, 1H, J1’Ha,
0
0
0
1 Hb = 11.6 Hz, J1’Hb,6 = 2.4 Hz, 20-Hb), 4.96 (dd, 1H, J8,8a = 7.3 Hz,
0
J4a,8a = 4.5 Hz, 8a-H), 6.24 (d, 1H, J4a,8a = 4.5 Hz, 4a-H), 7.77 (d, 2H,
J = 8.4 Hz, ArH), 8.29 (d, 2H, J = 8.4 Hz, ArH). 13C NMR (DMSO-d6):
d = 36.8, 40.3, 45.3, 67.5, 71.5, 72.7, 77.9, 121.5, 126.6, 133.9,
148.9, 164.7, 201. (FAB) m/z = 384 [MH+]. Anal. Calcd for
C15H17N3O7S: C, 46.99; H, 4.47; N, 10.96. Found: C, 47.30; H,
4.15; N, 10.73.
Acknowledgements
We sincerely thank the DST, Govt. of India, for financial support
(DST File No. SR/S1/OC-65/2006) and SAIF, CDRI, Lucknow, for pro-
viding microanalyses and spectral data.
3.2.12. Compound 5f
Pale yellow powder; mp 128–130 °C. IR (KBr):
m
= 3341, 3325,
1685, 1671, 1145, 692 cmꢁ1
.
1H NMR (400 MHz; DMSO-d6 + D2O):
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