α,β-Unsaturated carboxylic acid derivatives. Part 18. Syntheses of geometric isomers of 3,6-dibenzylidene- and 3-p-anisylidene-6-benzylidene-2,5-piperazinediones

Abstract

Naturally occurring 3,6-dibenzylidene- and 3-p-anisylidene-6-benzylidene-2,5-piperazinediones and their geometric isomers were synthesized by the condensation of 1-acetyl or 1,4-diacetyl derivative of (E)- and (Z)-benzylidene- or p-anisylidene-2,5-piperazinediones with an appropriate aldehyde. The configuration of these compounds were assigned on the basis of the spectroscopic analyses, and those of natural products were determined to be (3Z,6Z).