Formation of Ethyl 1-Thiomannopyranosides from 2-O-Chloroacetylated and 2-O-Levulinoylated Synthons
作者:Roberto Adamo、Pavol Kováč
DOI:10.1002/ejoc.200600139
日期:2006.6
bearing participating 2-O-chloroacetyl or 2-O-levulinoyl groups were treated with EtSH and BF3·Et2O. While poor stereoselectivity of the formation of ethyl 1-thioglycosides (α:β = 3:2) was observed with 2-O-chloroacetylated intermediates, the same products can be obtained with good stereoselectivity (α:β = 7:1) from 2-O-levulinoylated intermediates. Selective regeneration of the carbonyl group from dithioketals
为了制备用于合成霍乱弧菌 O:1 的 O 特异性多糖片段的关键糖基供体,对带有参与的 2-O-氯乙酰基或 2-O-乙酰丙酰基基团的过罗胺的 1-O-乙酰基衍生物进行了处理与 EtSH 和 BF3·Et2O。虽然使用 2-O-氯乙酰化中间体观察到形成乙基 1-硫糖苷 (α:β = 3:2) 的立体选择性较差,但可以从 2 以良好的立体选择性 (α:β = 7:1) 获得相同的产物-O-乙酰丙酸化中间体。还描述了在 S,O-缩醛存在下,通过在 MeCN/H2O 中用 AgNO3 和 Ag2O 处理,从二硫缩酮中选择性再生羰基。该转化允许由乙酰丙酸酯基团保护的碳水化合物直接制备 1-硫糖苷。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,