The asymmetric totalsynthesis of (-)-azaspirene, an angiogenesis inhibitor, has been accomplished, establishing its absolute stereochemistry. The key steps are a MgBr2.OEt2-mediated, diastereoselective Mukaiyama aldol reaction, a NaH-promoted, intramolecular cyclization of an alkynylamide, and the aldol reaction of a ketone containing functionalized gamma-lactam moiety without protection of tert-alcohol
The enantioselectivesynthesis of (−)-α-conhydrine has been achieved by two different synthetic routes. The key steps include Sharpless asymmetric dihydroxylation, regioselective opening of a cyclic sulfate and Wittig olefination.
Zn-Catalyzed Asymmetric Allylation for the Synthesis of Optically Active Allylglycine Derivatives. Regio- and Stereoselective Formal α-Addition of Allylboronates to Hydrazono Esters
have developed Zn-catalyzed asymmetricallylation of hydrazonoesters with allylboronates. The reactions proceeded smoothly in high yields and high stereoselectivities. Remarkably, formal α-addition occurred for α-substituted allylboronates exclusively, and excellent stereoselectivities were observed. This is the first example of catalytic regio- and stereoselective allylations with formal α-addition.
Enantioselective synthesis of (−)-α-conhydrine via cyclic sulfate methodology
作者:SubbaRao V. Kandula、Pradeep Kumar
DOI:10.1016/s0040-4039(03)00031-5
日期:2003.2
An asymmetric synthesis of (−)-α-conhydrine is described using the Sharpless asymmetric dihydroxylation and the regiospecific nucleophilic opening of a cyclic sulfate as the key steps.
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.