Studies on alpha-sialylation using sialyl donors with an auxiliary 3-thiophenyl group

被引：20

作者：

Martichonok, V ^{[1
]}

Whitesides, GM ^{[1
]}

机构：

[1] HARVARD UNIV,DEPT CHEM,CAMBRIDGE,MA 02138

来源：

CARBOHYDRATE RESEARCH | 1997年 / 302卷 / 3-4期

关键词：

stereoselective alpha-sialylation; thioglycoside; phenylsulfenyl triflate; sialyl glycoside;

D O I：

10.1016/S0008-6215(97)00094-3

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

Reaction of the methyl ester of 2-chloro-3-S-phenyl-3-thiosialic acid (4) with sodium thiomethoxide in acetonitrile at 0 degrees C affords the methyl ester of 2-S-methyl-3-S-phenyl-2,3-dithio-alpha-sialic acid (6a) in quantitative yield. Sialylation of tetrahydropyran-2-methanol (7) and 2-(trimethylsilyl)ethyl 2,2',3,6,6'-penta-O-benzyl-alpha-lactoside (8) with 6a in the presence of phenylsulfenyl triflate (PST) as promotor in CH3CN at -40 degrees C gives alpha-sialosides 9 and 10 in good yield and excellent stereoselectivity. No beta-sialosides are formed in either case. Acetylation of product 10, and the subsequent reductive removal of the 3-thiophenyl group using Ph3SnH, affords 12 - protected GM3 trisaccharide - in 82% yield after two steps. Sialylation of acceptor 8 with chloride 4 using silver triflate as promotor afforded 10 in 48% yield after two days at -15 degrees C in THF. A possible mechanism of sialylation with 6a that involves intermediate alpha- and beta-nitrilium ions is discussed. (C) 1997 Elsevier Science Ltd.

引用

页码：123 / 129

页数：7

共 26 条

[1] ALPHA-SELECTIVITY AND GLYCAL FORMATION ARE TEMPERATURE-DEPENDENT IN GLYCOSYLATION WITH SIALIC-ACID - SYNTHESIS OF A NEU5AC-ALPHA(2-6)GAL THIOGLYCOSIDE BUILDING BLOCK [J].