A stereoselective method has been elaborated for the synthesis of oxime esters, (-)-4a, b, from which, as common intermediates, (+)-apovincaminic acid esters (3a,b), (+)-vincamine (1) and (-)-vincamone (2) can be prepared.
Starting from l-tryptophan two chiral syntheses of the 3S, 17S-lactam 11, an intermediate for the preparation of (+)-vincamine and its derivatives, were elaborated in good overall yield and with an optical purity of 96%.
Formal enantioselective synthesis of (+)-vincamine. The first enantioselective route to (+)-3,14-epivincamine and its enantiomer
作者:José C.F Alves、Alessandro B.C Simas、Paulo R.R Costa
DOI:10.1016/s0957-4166(98)00489-3
日期:1999.1
A formal synthesis of (+)- vincamine (1) from (S)-(+)- 2-ethyl-2-(2-methoxycarbonylethyl) cyclopentanone (6a) is described. This intermediate had previously been obtained by our research group in 90% ee through d'Angelo's deracemizing alkylation of the chiral imine 7, easily prepared from (R)-(+)-alpha-methylbenzylamine and 2-ethyl cyclopentanone with methyl acrylate. A potencial advanced intermediate for the synthesis of (+)-4, an epimer of (+)-1 at positions C-3 and C-14, has also been prepared from 6a. (C) 1999 Elsevier Science Ltd. All rights reserved.