Abstract
(Z)-3-(2, 4, 5-Trimethoxy-3-methylbenzylidene)-1, 6-dimethylpiperazine-2, 5-dione (7a) was prepared by a simple regioselective C-monomethylation of (Z)-4-(4-methoxybenzyl)-3-(2, 4, 5-trimethoxy-3-methylbenzylidene)-1-methyl-piperazine-2, 5-dione (3) followed by deprotection. Compound 7a was also prepared from (S)-1, 4-diacetyl-3-methylpiperazine-2, 5-dione (8) and the benzaldehyde derivative (9) in five steps as an optically active form. It was shown to be a useful intermediate for the preparation of novel octahydro-1, 5-imino-3-benzazocin-4, 7, 10-trione derivatives having a methyl group at the C-2 position, as ABC ring models of saframycins.
