Aldol Reactions with Erythrulose Derivatives: Stereoselective Synthesis of Differentially Protected syn -α,β-Dihydroxy Esters
摘要:
Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-alpha,beta-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent. (C) 2000 Elsevier Science Ltd. All rights reserved.
Aldol Reactions with Erythrulose Derivatives: Stereoselective Synthesis of Differentially Protected syn -α,β-Dihydroxy Esters
摘要:
Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-alpha,beta-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent. (C) 2000 Elsevier Science Ltd. All rights reserved.
We have investigated the formation of various metal enolates of 1-O-silylated erythrulose 3,4-acetonides. We were able to prepare boron enolates using Brown's dicyclohexylboron chloride/tertiary amine system. When these enolates were allowed to react with a range of achiral aldehydes, highly stereoselective aldol additions took place with formation of the syn/syn stereoisomer. This has been attributed to the exclusive formation of a Z boron enolate, which is in a sharp contrast with the usual behaviour of the aforementioned reagent. (C) 1999 Elsevier Science Ltd. All rights reserved.
Aldol Reactions with Erythrulose Derivatives: Stereoselective Synthesis of Differentially Protected syn -α,β-Dihydroxy Esters
作者:M. Carda、J. Murga、E. Falomir、F. González、J.A. Marco
DOI:10.1016/s0040-4020(99)01041-8
日期:2000.1
Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-alpha,beta-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent. (C) 2000 Elsevier Science Ltd. All rights reserved.