Lewis acid- and cationic lithium-mediated diastereoselective aldol-type reaction based on a double chiral recognition manner for the asymmetric synthesis of α-substituted serines
作者:Shigeki Sano、Xiao-Kai Liu、Maki Takebayashi、Yoshimaro Kobayashi、Keiko Tabata、Motoo Shiro、Yoshimitsu Nagao
DOI:10.1016/0040-4039(95)00725-r
日期:1995.6
Diastereoselective aldol-type reaction of ethyl (5R or 5S)-3,6-diethoxy-2,5-dihydro-5-isopropyl-2-pyrazinecarboxylate (5) with chiral aldehyde 7 was investigated by using Sn(OSO2CF3)(2)-N-ethylpiperizine, MgBr2-Et(3)N, n-butyllithium, and lithium diisopropylamide. The mediation mode with Sn(II) between (5R or 5S)-5 and 7 proved to be quite different from that with Mg(II). The two aldol products were converted to the corresponding gamma-lactonic alpha-substituted serines (2S)- and (2R)-10.