INVESTIGATIONS OF THE BIOSYNTHESIS OF SESBANINE AND CORONATINE

[摘要] Sesbanine (5) is a novel cytotoxic alkaloid that was isolated from seed extracts of Sesbania drumondii $sp{1,2}$ (Leguminosae). The biosynthesis of sesbanine was approached by dividing the molecule into two moieties, the pyridine ring moiety (A) and the cyclopentanol ring moiety (C). Evidence is offered which indicates that the pyridine ring moiety (A) arises from one unit of nicotinic acid. It was demonstrated that nicotinic acid is derived from tryptophan in Sesbania and that tryptophan also serves as a specific precursor of sesbanine via nicotinic acid. The cyclopentanol moiety (C) was shown to be derived from shikimic acid via p-hydroxybenzoic acid.Investigations of the biosynthesis of the unusual phytotoxic coronatine (20) have shown that the toxin is formed in a novel manner. It has been demonstrated that the hydrindanone moiety (21) of the toxin is assembled from the head to tail linkage of five acetate units with C-2 and C-3 of pyruvate serving as a starter unit. The mechanism for formation of the C-C single bonds between C-3 of pyruvate and C-2 of two acetate units is presently obscure. The 1-amido-1-carboxy-2-ethylcyclopropyl moiety (22) of the toxin is derived by an unprecedented cyclization of the amino acid isoleucine.

[发布机构] Rice University

[效力级别] chemistry