Synthesis of Vinca alkaloids and related compounds. Part 18. Stereochemical investigations on some intermediates leading to (+)-vincamine

Abstract

The C-2′ absolute configurations of hydroxy esters (1) and (2) have been determined by X-ray analysis. The absolute configurations at C-15 of several compounds with the E-homoeburnane skeleton [(3)–(6)] and the relative configurations at C-14 and –15 of compounds (8) have been elucidated. The dominant conformation of compounds (3)—(7) have been established on the basis of 13C n.m.r. and c.d. spectroscopic results. A new methods has been elaborated for the preparation of oxime (10), a compound of importance in the synthesis of Vinca alkaloids.