Dehydroxy Substitution Reactions of the Anomeric Hydroxy Groups in Some Protected Sugars Initiated by Anodic Oxidation of Triphenylphosphine.
作者:Hatsuo MAEDA、Sayaka MATSUMOTO、Takashi KOIDE、Hidenobu OHMORI
DOI:10.1248/cpb.46.939
日期:——
The anodic transformation of 2, 3 : 5, 6-di-O-isopropylidene-α-D-mannofuranose (4) and 2, 3, 4, 6-tetra-O-benzyl-D-glucopyranose (5) to the corresponding alkoxy phosphonium ions induces dehydroxy substitution of the sugars at the anomeric positions. Their dehydroxy fluorination and chlorination has been achieved by constant-current electrolysis with CH2Cl2-1, 2-dimethoxyethane/Ph3P/Ph3PH·BF4 and with CH2Cl2/Ph3P/Et4N·Cl, respectively.The electrolysis in the presence of Ph3P has proved to serve O-glycosylation with 4 or 5 as a glycosyl donor, provided that an aliphatic alcohol as a glycosyl acceptor is a weaker nucleophile, such as (CF3)2CHOH, CF3CH2OH, and tert-BuOH, than the protected sugar toward Ph3P+· generated anodically from Ph3P. The present electrochemical reactions for 2, 3, 4, 6-tetra-O-acetyl-D-glucopyranose were unsuccessful, except for the dehydroxy chlorination.
将 2, 3 : 5, 6-二-O-异亚丙基-α-D-甘露糖(4)和 2, 3, 4, 6-四-O-苄基-D-吡喃葡萄糖(5)阳极转化为相应的烷氧基鏻离子,可诱导糖类在异构体位置发生脱羟基取代。分别用 CH2Cl2-1,2-二甲氧基乙烷/Ph3P/Ph3PH-BF4 和 CH2Cl2/Ph3P/Et4N-Cl 进行恒流电解,实现了它们的脱羟基氟化和氯化。事实证明,以 4 或 5 为糖基供体,在 Ph3P 存在下进行的电解可用于 O-糖基化,前提是作为糖基受体的脂肪醇(如 (CF3)2CHOH、CF3CH2OH 和 tert-BuOH)比受保护的糖对 Ph3P 阳极生成的 Ph3P+- 的亲核力更弱。除了脱羟基氯化反应外,2, 3, 4, 6-四-O-乙酰基-D-吡喃葡萄糖的电化学反应都不成功。