A Stereodivergent Approach to 5a-Carba-α-D-gluco-, -α-D-galacto and -β-L-gulopyranose Pentaacetates fromD-Mannose, Based on 6-exo-dig Radical Cyclization and Barton−McCombie Radical Deoxygenation
作者:Ana M. Gómez、Eduardo Moreno、Serafín Valverde、J. Cristóbal López
DOI:10.1002/ejoc.200300339
日期:2004.4
The three carbasugars, 5a-carba-α-D-gluco-, -α-D-galacto and -β-L-gulopyranose pentaacetates 42, 35 and 28 respectively, have been prepared in a stereodivergent manner from D-mannose. Alkynyl derivatives of 2,3:4,6-di-O-isopropylidene-D-mannopyranose, which are homologated at C-1 by reaction with trimethylsilylacetylide, undergo a 6-exo-dig radical cyclization, from a radical located at C-5, to yield
三种碳水化合物,5a-carba-α-D-葡萄糖-、-α-D-半乳糖和-β-L-吡喃葡萄糖五乙酸酯分别为 42、35 和 28,已从 D-甘露糖以立体发散方式制备。2,3:4,6-二-O-异亚丙基-D-吡喃甘露糖的炔基衍生物,通过与三甲基甲硅烷基乙炔反应在C-1处同系化,从位于C-的自由基经历6-exo-dig自由基环化5,得到高度官能化的外-亚甲基环己烷的混合物。后者中环外双键的臭氧分解产生环己酮,通过羰基部分的立体选择性还原,然后在 C-4 或 C-5a 位(母体碳水化合物编号)进行位点选择性脱氧,得到标题碳糖。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)