R. Kumar, P. Tiwari, P. R. Maulik, A. K. Misra
SHORT COMMUNICATION
20.7 ppm. IR (neat): ν = 2952, 1747, 1417, 1591, 1384, 1228, 1074,
˜
Experimental Section
1037, 719 cm–1. ESI-MS: 550 [M + Na]+. C26H25NO9S (527.1): C
Typical Experimental Procedure for the Preparation of Per-O-acety-
lated Thioglycosides
59.19, H 4.78; found C 58.95, H 5.0.
Ethyl 3,4,6-Tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopy-
ranoside (2n): Yield 92%, oil. [α]2D5 = +90.5 (c = 1.5, CHCl3). 1H
NMR (CDCl3, 300 MHz): δ = 7.81–7.65 (m, 4 H, Ar-H), 5.80–5.71
(t, J = 9.6 Hz, 1 H, 3-H), 5.42 (d, J = 10.6 Hz, 1 H, 1-H), 5.15–
5.05 (t, J = 9.6 Hz, 1 H, 4-H), 4.37–4.26 (t, J = 10.4 Hz, 1 H, 2-
H), 4.20–4.02 (dq, 2 H, 6-Ha,b), 3.87–3.80 (m, 1 H, 5-H), 2.70–2.50
(q, 2 H, SCH2CH3), 2.02, 1.95, 1.78 (3×s, 9 H, 3×COCH3), 1.17–
1.10 (t, J = 7.5 Hz, 3 H, SCH2CH3) ppm. 13C NMR (CDCl3,
75 MHz): δ = 170.9, 170.4, 169.8, 168.0, 167.5, 134.7, 131.9, 131.6,
124.0 (3 C), 81.5, 76.3, 71.9, 69.3, 62.3, 54.1, 24.6, 21.0, 20.9, 20.7,
Phenyl 2,3,4,6-Tetra-O-acetyl-1-thio-β-D-galactopyranoside (2d): A
suspension of d-galactose (1.8 g, 10.0 mmol) in acetic anhydride
(4.82 mL, 51.0 mmol) was placed in an ice bath with continuous
stirring. HBr/AcOH (30%, 2.7 mL, 10.0 mmol) was added in one
portion to the cold suspension. An exothermic reaction started im-
mediately and the reaction mixture was allowed to stir at room
temperature until a clear solution was obtained (approx. 15 min).
The reaction mixture was cooled to 0 °C, additional HBr/AcOH
(30%, 5.4 mL, 20 mmol) was added slowly, and stirring was contin-
ued for 2 h at room temperature. After completion of the reaction
(monitored by TLC; hexane/EtOAc 1:1), solvents were removed un-
der reduced pressure and coevaporated with toluene. Thiophenol
(1.5 mL, 14.6 mmol), tetrabutylammonium hydrogen sulfate
(TBAHS) (510 mg, 1.5 mmol) and aq. Na2CO3 (1 m, 70 mL) were
added successively to a solution of the crude mass in CH2Cl2
(50 mL) and the two-phase reaction mixture was allowed to stir
vigorously for another 30 min. The reaction mixture was diluted
with CH2Cl2 (50 mL). The organic layer was separated and washed
with water, dried (Na2SO4), and concentrated under reduced pres-
sure. Purification of the crude reaction product over SiO2 with hex-
ane/EtOAc (4:1) furnished pure 2d, which was further crystallized
from Et2O/hexane (4.0 g, 91%). A series of thioglycosides was pre-
pared by a similar reaction procedure (Table 1).
15.2 ppm. IR (neat): ν = 2965, 1753, 1413, 1597, 1380, 1236, 1070,
˜
1042, 736 cm–1. ESI-MS: 502 [M + Na]+. C22H25NO9S (479.1): C
55.11, H 5.26; found: C 55.35, H 5.48.
2,3,4-Tri-O-acetyl-6-deoxy-α-L-mannopyranosyl Azide (4d): Yield
85%, oil. [α]2D5 = –163 (c = 1.2, CHCl3). 1H NMR (200 MHz,
CDCl3): δ = 5.32–5.31 (d, J = 1.4 Hz, 1 H, 1-H), 5.24–5.20 (m, 1
H, 2-H), 5.15–5.03 (m, 2 H, 3-H and 4-H), 4.10–3.96 (m, 1 H, 5-H),
2.16, 2.06, 1.99 (3×s, 9 H, 3×COCH3), 1.29–1.26 (d, J = 6.2 Hz, 3
H, CH3) ppm. 13C NMR (50 Hz, CDCl3): δ = 170.21 (3 C), 87.85,
70.81, 69.80, 68.97, 68.66, 21.11, 21.06, 20.93, 17.77 ppm. IR
(neat): ν = 2116, 1749, 1374, 1243, 1124, 1046, 936, 758 cm–1. ESI-
˜
MS: 338 [M + Na]+. C12H17N3O7 (315.1): C 45.71, H 5.43; found
C 45.48, H 5.60.
2,3,4-Tri-O-acetyl-β-L-arabinopyranosyl Azide (4g): Yield 90%, pale
Typical Experimental Procedure for the Preparation of Per-O-acety-
lated Glycosyl Azides
yellow solid; m.p. 105 °C. [α]2D5 = –5.4 (c = 1.2, CHCl3). H NMR
(CDCl3, 300 MHz): δ = 5.30–5.23 (m, 1 H, 2-H), 5.18–4.97 (m, 2
H, 3-H and 4-H), 4.57–4.53 (d, J = 7.3 Hz, 1 H, 1-H), 4.12–4.04
(dd, J = 2.8 and 13.1 Hz, 1 H, 5-Ha), 3.78–3.71 (dd, J = 1.5 and
13.1 Hz, 1 H, 5-Hb), 2.16, 2.10, 2.01 (3×s, 9 H, 3×COCH3) ppm.
13C NMR (CDCl3, 75 MHz): δ = 170.6, 170.4, 169.7, 88.8, 70.0,
1
2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl Azide (4b): A suspen-
sion of d-galactose (1.8 g, 10.0 mmol) in acetic anhydride (4.82 mL,
51.0 mmol) was placed in an ice bath with continuous stirring.
HBr/AcOH (30%, 2.7 mL, 10.0 mmol) was added in one portion
to the cold suspension of the reaction mixture. An exothermic reac-
tion started immediately and the reaction mixture was allowed to
stir at room temperature until a clear solution was obtained (ap-
prox. 15 min). The reaction mixture was cooled to 0 °C, additional
HBr/AcOH (30%, 5.4 mL, 20 mmol) was added slowly, and stirring
was continued for 2 h at room temperature. After completion of
the reaction (monitored by TLC; hexane/EtOAc 1:1), solvents were
removed under reduced pressure and coevaporated with toluene.
Sodium azide (1.3 g, 20 mmol), tetrabutylammonium hydrogen sul-
fate (TBAHS) (510 mg, 1.5 mmol) and aq. Na2CO3 (1 m, 70 mL)
were added successively to a solution of the crude mass in CH2Cl2
(50 mL) and the two-phase reaction mixture was allowed to stir
vigorously for another 1.5 h. The reaction mixture was diluted with
CH2Cl2 (50 mL). The organic layer was separated and washed with
water, dried (Na2SO4), and concentrated under reduced pressure.
Purification of the crude reaction product over SiO2 with hexane/
EtOAc (3:1) furnished pure 4b, which was further crystallized from
Et2O/hexane (3.17 g, 85%). A series of glycosyl azides was prepared
by a similar reaction procedure (Table 2).
68.3, 67.4, 65.5, 20.7, 20.5, 20.3 ppm. IR (neat): ν = 2124, 1757,
˜
1370, 1249, 1132, 1046, 940, 757 cm–1. ESI-MS: 324 [M + Na]+.
C11H15N3O7 (301.1): C 43.86, H 5.02; found C 43.67, H 5.28.
Acknowledgments
Instrumentation facilities from SAIF, CDRI are gratefully ac-
knowledged. R. K. and P. T. thank the DOD and CSIR, New
Delhi, for providing fellowships. This project was partly funded
by the Department of Science and Technology (DST), New Delhi
(Project no. SR/FTP/CSA-10/2002), India.
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Spectral Data for Compounds not Reported Earlier
Phenyl 3,4,6-Tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-gluco-
pyranoside (2m): Yield 90%, oil. [α]2D5 = +70.5 (c = 1.5, CHCl3). 1H
NMR (CDCl3, 300 MHz): δ = 7.88–7.74 (m, 4 H, Ar-H), 7.43–7.26
(m, 5 H, Ar-H), 5.86–5.76 (t, J = 10.1 Hz, 1 H, 3-H), 5.80–5.71 (t,
J = 10.0 Hz, 1 H, 4-H), 5.19–5.10 (t, J = 10.0 Hz, 1 H, 2-H), 4.41–
4.36 (d, J = 10.4 Hz, 1 H, 1-H), 4.35–4.23 (m, 2 H, 6-Ha,b), 3.95–
3.87 (m, 1 H, 5-H), 2.10, 2.02, 1.84 (3×s, 9 H, 3×COCH3) ppm.
13C NMR (CDCl3, 75 MHz): δ = 170.9, 170.4, 169.8, 168.1, 167.3,
134.8–124.0 (C arom.), 83.4, 76.3, 72.0, 69.1, 62.6, 53.9, 21.1, 20.9,
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Eur. J. Org. Chem. 2006, 74–79