Serine and Threonine Schiff Base Esters React with β-Anomeric Peracetates in the Presence of BF<sub>3</sub>·Et<sub>2</sub>O to Produce β-Glycosides
作者:Charles M. Keyari、Robin Polt
DOI:10.1080/07328303.2010.508295
日期:2010.5
and more efficient alternatives to published methods. L-serine or L-threonine benzyl ester hydrochloride salts were reacted with the diarylketimine bis-(4-methoxyphenyl)-methanimine in CH3CN at rt to form the more nucleophilic Schiff bases 3a and 3b in excellent yield. These Schiff bases exhibited ring-chain tautomerism in CDCl3 as shown by 1H NMR. Schiff bases 3a and 3b, acting as glycosyl acceptors
据报道,利用活化的席夫碱糖基受体对L-丝氨酸和L-苏氨酸的糖基化进行了改进的方法,这是已公开方法的较便宜且更有效的替代方法。使L-丝氨酸或L-苏氨酸苄基酯盐酸盐与CH 3 CN中的二芳基酮亚胺双-(4-甲氧基苯基)-甲亚胺在室温下反应,以优异的产率形成更具亲核性的席夫碱3a和3b。如1 H NMR所示,这些席夫碱在CDCl3中表现出环链互变异构现象。希夫碱3a和3b充当糖基受体,在室温下与简单的过乙酸乙酸供体反应,并以BF3·OEt2促进,以优异的收率和纯度提供相应的L-丝氨酸和L-苏氨酸O-连接的糖苷。二肽酯Schiff碱Ar2C = N-Ser-Val-OCH3 3e也反应生成β-糖苷,收率极高,且没有差向异构化。用微波辐射,反应在2至5分钟内完成。为了进一步研究该反应,研究了经典的AgOTf促进的D-吡喃葡萄糖基,乳糖基和麦芽糖基溴化物的Koenigs-Knorr反应,提供了35%至