Stereoselectivity in (Z)-Vinylmetal Additions to the Dictyostatin C1-C9 β-Silyloxy Aldehyde
作者:Andrea Ambrosi、Luca Pignataro、Chiara Zanato、Cesare Gennari
DOI:10.1002/ejoc.201101201
日期:2012.1
vinyllithium additions. The configuration of the newly created C9 stereocenter was assigned through Rychnovsky's acetonide 13C NMR method. The diastereoselectivity in this particular type of (Z)-vinylmetal addition reaction appears to be controlled by a subtle balance between the intrinsic stereochemical preference of the β-silyloxy aldehyde (1,3-anti-selective) and that of the chiral lithium (Z)-vinylzincates
(Z) -乙烯基碘化物 6a - d 以高收率合成,具有良好的非对映选择性和对映选择性,使用 Marshall-Tamaru,Pd 催化的烯基锌反应作为关键步骤。通过乙烯基锂和乙烯基锌酸锂路线将 6a-d 添加到 dictyostatin C1-C9 β-甲硅烷氧基醛 5。与相应的乙烯基锂添加相比,乙烯基锌酸锂的添加总是以更高的产率进行并且产生更少的副产物。新创建的 C9 立体中心的配置是通过 Rychnovsky 的 acetonide 13C NMR 方法分配的。这种特定类型的 (Z) - 乙烯基金属加成反应中的非对映选择性似乎受 β-甲硅烷氧基醛(1,3-反选择性)和手性锂(Z ) 乙烯基锌酸盐。