4526
A. Sethi et al. / Bioorg. Med. Chem. 15 (2007) 4520–4527
gave 14 (1 g, 57.4%) (2,3,4-tri-O-acetyl-L-rhamnose) as
a syrup. To a solution 14 (700 mg, 2.4 mmol) in dry
dichloromethane (25 mL) was added anhydrous potas-
sium carbonate (350 mg) and trichloroacetonitrile
(2.4 mL, 24 mmol). The suspension was stirred for
48 h at room temperature under nitrogen atmosphere.
The mixture was filtered over Celite, washed with
dichloromethane (20 mL) and the filtrate concentrated
under reduced pressure. The residue was purified to
References and notes
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give 15 (2,3,4-tri-O-acetyl-a-L-rhamnopyranosyl tri-
25
D
chloroacetimidate) as a yellow syrup. ½aꢂ ꢀ50.0 (c
1.0, CHCl3). It was further identified by its 1H
NMR. To a stirred mixture of 5 (200 mg, 0.53 mmol)
˚
and 4 A molecular seives in dichloromethane (15 mL)
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idue (CHCl3:MeOH, 95:5) afforded pure compound
20.
5.7.1. 16a-[(2,3,4-tri-O-Acetyl-a-L-rhamnopyranosyl)oxy-
25
D
ethoxy]3b-hydroxy pregn-5-en-20-one (20). Syrupy, ½aꢂ
+66.6 (c 0.75, MeOH); IR (KBr) mmax 3435, 2955, 1720,
1665 cmꢀ1; H NMR (CDCl3, 300 MHz) d (ppm) 5.34–
1
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5.30 (2H, m, H-20, H-30), 5.28–5.27 (1H, m, H-6); 5.09
(1H, t, H-40, J = 9.2Hz), 4.76 (1H, s, H-10), 4.49–4.45
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(3H, s, OAc), 1.23 (3H, d, CH3-60, J = 6.3 Hz), 1.05
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16a-[(2,3,4,6-tetra-O-Acetyl-a-D-mannopyrano-
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25
upy, ½aꢂ +28.0 (c 0.50, MeOH); IR (KBr) mmax 3440,
D
2990, 1710, 1645 cmꢀ1; H NMR (CDCl3, 200 MHz) d
(ppm) 5.35 (m, 1H, H-6), 5.33–5.11 (m, 2H, H-30, H-
40), 5.02 (s, 1H, H-10), 4.96 (m, d, H-20, J = 2Hz),
4.62–4.57 (m, 1H, H-50), 4.57–4.46 (m, 1H, H-16),
4.32–4.28 (m, 2H, H-60), 4.24–4.06 (m, 4H, m, OCH2
CH2O), 3.59–3.45 (m, 1H, H-3), 2.59 (d, 1H, H-17,
J = 6.0Hz), 2.18 (s, 3H, CH3-21), 2.09 (s, 3H, OAc),
2.06 (3, 3H, OAc), 2.033 (s, 3H, OAc), 2.005 (s, 3H
OAc), 1.01 (s, 3H CH3-19), 0.64 (s, 3H, CH3-18). MS
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1
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Acknowledgments
The authors are grateful to the RSIC division of
the central drug research institute and the Director
of the CIMAP, Lucknow, India for the analytical
data.
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