Competitive formation of peracetylated α- l -arabinopyranosides and β- l -arabinopyranose 1,2-(alkyl orthoacetates) in Koenigs-Knorr condensations
作者:Volker Magnus、Drazˇen Vikić-Topić、Sonja Iskrić、Sergije Kveder
DOI:10.1016/0008-6215(83)88188-9
日期:1983.4
Abstract Mixtures of peracetylated β- l -arabinopyranose 1,2-(alkyl orthoacetates) and the corresponding α- l -arabinopyranosides, in ratios as high as 1:1.3, have been obtained from primary, secondary, and tertiary alcohols and 2,3,4-tri- O -acetyl-β- l -arabinosyl bromide, by reaction in dichloromethane-diethyl ether (3:1) in the presence of silver oxide and anhydrous calcium sulfate. Orthoester formation
摘要从伯,仲和叔醇和2,3中获得了比例高达1:1.3的过乙酰化β-1-阿拉伯吡喃葡萄糖1,2-(原乙酸烷基酯)与相应的α-1-阿拉伯吡喃糖苷的混合物。在氧化银和无水硫酸钙存在下,在二氯甲烷-乙醚(3:1)中反应,生成4-4-三-O-乙酰基-β-1-阿拉伯糖基溴化物。当用极性较小的氯仿或四氯化碳代替二氯甲烷时,以及用体积较大的二丁基或二异丙基醚代替乙醚时,原酸酯的形成减少。产物分布对于在氧化银存在下涉及1,2-顺式酰基糖基卤化物的Koenigs-Knorr缩合反应是不寻常的,