The first semi-synthesis of enantiopure homoharringtonine via anhydrohomoharringtonine from a preformed chiral acyl moiety
作者:Jean-Pierre Robin、Robert Dhal、Gilles Dujardin、Laurent Girodier、Laurence Mevellec、Sandrine Poutot
DOI:10.1016/s0040-4039(99)00327-5
日期:1999.4
(2'R,3S,4S,5R)-(-)-Homoharringtonine 2 was synthesized by direct esterification of cephalotaxine, using the activated forms of suitably substituted tetrahydropyrancarboxylic acids as sterically compact chiral side-chain precursors, followed by selective ring opening of the resulting (2'R,3S,4S,5R)-(-)-anhydrohomoharringtonine 6. Both enantiomers of the anhydro acyl moiety were prepared either by asymmetric alpha-hydroxyalkylation of the suitably substituted ethylenic alpha-ketoester 7 followed by acidic cyclisation, or by resolving the corresponding racemic mixture via formation of diastereomers with (-)quinine. Racemic cephalotaxine, as well as both its enantiomers, were prepared from natural -partially racemized- (-)-cephalotaxine 1. (C) 1999 Elsevier Science Ltd, All rights reserved.
(2'R,3S,4S,5R)-(-)-齐墩果酸甲酯 2 由 cephalotaxine 直接酯化制得,采用适当取代的四氢吡喃甲酸的活化形式作为立体紧凑的手性侧链前体,随后通过选择性开环得到相应的 (2'R,3S,4S,5R)-(-)-anhydrohomoharringtonine 6。干酰基部分的两个对映体通过以下两种方法制备:一种方法是对适当取代的烯基 α-酮酯 7 进行不对称 α-羟基烷基化,然后进行酸性环化;另一种方法是通过对 (-)-金鸡纳碱形成非对映异构体来分离对应的外消旋混合物。外消旋 cephalotaxine 以及其两个对映体均由天然的部分外消旋的 (-)-cephalotaxine 1 制得。版权 © 1999 Elsevier Science Ltd,保留所有权利。