Expedient Synthesis of an Anomerically Modified Trisaccharide Component of the Capsular Polysaccharide from<i>Streptococcus pneumoniae</i>Type 19F
作者:Eisuke Kaji、Eiko Matsui、Mie Kobayashi、Shonosuke Zen
DOI:10.1246/bcsj.68.1449
日期:1995.5
A practical stereoselective synthesis is described for α-d-ManNAc-(1→4)-α-d-Glc-(1→2)-l-Rha, an anomerically modified trisaccharide component of the capsular polysaccharide of Streptococcus pneumoniae type 19F. The key intermediary disaccharide, 2-(benzoyloxyimino)-2-deoxyglycosyl-α(1→4)-glucoside, was prepared by α-selective glycosylation (AgOTf–TMU/CH2Cl2, 90%) of a suitably blocked p-methoxybenzyl 2,3,6-tri-O-benzyl-β-d-glucopyranoside with 3,4,6-tri-O-benzoyl-2-(benzoyloxyimino)-2-deoxy-α-d-arabino-hexopyranosyl bromide, and converted into an α-d-ManNAc-(1→4)-α-d-Glc-(1→MBn) derivative by means of a manno-selective reduction (BH3·THF → Ac2O, 55%). Consecutive anomeric activation (1-OMBn → 1-OH → 1-F, 45% over 2 steps), glycosylation (SnCl2–AgClO4/CH2Cl2, 71%, α : β = 2 : 1) of 2-OH of benzyl 3,4-di-O-benzyl-α-l-rhamnopyranoside, and deblocking (NaOMe → Pd-C/H2, 90%) gave the target trisaccharide.
本研究描述了一种实用的立体选择性合成方法,用于合成肺炎链球菌 19F 型胶囊多糖中的α-d-ManNAc-(1→4)-α-d-Glc-(1→2)-l-Rha,这是一种经同分异构体修饰的三糖成分。2-(benzoyloxyimino)-2-deoxyglycosyl-α(1→4)-glucoside 是通过对甲氧基苄基 2,3,6-三-O-苄基-β-d-吡喃葡萄糖苷与 3、3,4,6-O-三苯甲酰基-2-(苯甲酰氧基亚氨基)-2-脱氧-α-d-阿拉伯吡喃糖基溴化物,并通过甘露选择性还原(BH3-THF → Ac2O,55%)转化为 α-d-ManNAc-(1→4)-α-d-Glc-(1→MBn) 衍生物。通过对 3,4-二-O-苄基-α-鼠李糖苷的 2-OH进行连续的异构活化(1-OMBn → 1-OH → 1-F,45%,共 2 步)、糖基化(SnCl2-AgClO4/CH2Cl2,71%,α : β = 2 : 1)和解锁(NaOMe → Pd-C/H2,90%),得到了目标三糖。