Download PDF
Synlett 2010(10): 1519-1524  
DOI: 10.1055/s-0029-1219943
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Direct α-Selective Glycosylations of Acetyl-Protected 2-Deoxy- and 2,6-Dideoxythioglycosides by Preactivation Protocol

Yin-Suo Lua,b, Qin Lia,b, Yuan Wanga,b, Xin-Shan Ye*a,b
a The State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Xue Yuan Rd No. 38, Beijing 100191, P. R. of China
b School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd No. 38, Beijing 100191, P. R. of China
Fax: +86(10)62014949; e-Mail: xinshan@bjmu.edu.cn;
Further Information

Publication History

Received 4 March 2010
Publication Date:
19 May 2010 (online)

   Permissions and Reprints All articles of this category
Preview

Abstract

An efficient preactivation protocol for the highly α-stereo­selective glycosylation of 2-deoxy- and 2,6-dideoxysugars has been developed using acetyl-protected 2-deoxy- and 2,6-dideoxythioglycosides as glycosyl donors. The approach allows a wide range of glycosyl acceptors and donors to be used.

Key words

preactivation - α-stereoselective glycosylation - 2-deoxy­glycosides - 2,6-dideoxysugars - carbohydrate

22

Typical Glycosylation Procedure
Triflic anhydride (11.0 µL, 0.061 mmol) was added to a stirred solution of p-methylphenyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-α-d-galactopyranoside (1a, 30.0 mg, 0.076 mmol), benzenesulfinyl morpholine (BSM, 12.9 mg, 0.061 mmol), and 4 Å MS (350 mg, activated powder) in CH2Cl2 (3.0 mL) at -72 ˚C under nitrogen atmosphere. The reaction mixture was stirred for 10 min. After loss of 1a detected by TLC, a solution of methyl 3-O-benzyl-4,6-O-benzylidene-α-d-glucopyranoside (2a, 18.8 mg, 0.051 mmol) in CH2Cl2 (0.5 mL) was added dropwise to the reaction mixture. The mixture was stirred for 30 min, and the reaction was quenched by Et3N (8.0 µL). The precipitate was filtered off, and the filtrate was concentrated. The residue was purified by column chromatography on silica gel (PE-EtOAc, 2.5:1) to give methyl 3-O-benzyl-4,6-O-benzylidene-2-O-(3,4,6-tri-O-acetyl-2-deoxy-α-d-galactopyranosyl)-α-d-gluco-pyranoside (3a, 27.6 mg, 84% yield) as a foam. R f  = 0.35 (PE-EtOAc, 1.5:1). ¹H NMR (500 MHz, CDCl3): δ = 7.50 (dd, 2 H, J = 2.0, 7.5 Hz), 7.40-7.33 (m, 7 H), 7.29-7.27 (m, 1 H), 5.60 (s, 1 H), 5.37 (ddd, 1 H, J = 3.0, 5.0, 12.5 Hz), 5.15 (d, 1 H, J = 3.0 Hz), 5.14 (d, 1 H, J = 3.5 Hz), 4.93 (d, 1 H, J = 10.5 Hz), 4.89 (d, 1 H, J = 3.5 Hz), 4.71 (d, 1 H, J = 10.5 Hz), 4.36 (t, 1 H, J = 6.5 Hz), 4.31 (dd, 1 H, J = 4.5, 10.0 Hz), 3.98 (t, 1 H, J = 9.5 Hz), 3.90 (dd, 1 H, J = 6.5, 11.0 Hz), 3.87-3.74 (m, 4 H), 3.65 (t, 1 H, J = 9.5 Hz), 3.43 (s, 3 H), 2.13-2.08 (m, 4 H), 2.00 (s, 3 H), 1.96-1.92 (m, 4 H). ¹³C NMR (125 MHz, CDCl3): δ = 170.13, 170.23, 169.79, 138.06, 137.26, 128.96, 128.54, 128.47, 128.25, 127.86, 125.95, 101.27, 97.12, 94.10, 82.71, 76.85, 75.74, 73.45, 69.00, 66.61, 65.87, 62.25, 61.87, 55.23, 29.86, 20.81, 20.70. MS (ESI-TOF, positive): m/z = 667 [M + Na]+. Anal. Calcd for C33H40O13: C, 61.48; H, 6.25. Found: C, 61.65; H, 6.40.