The marticins: confirmation of structure, elucidation of biosynthetic origin by 13Cmr studies, and revision of stereochemical assignments

Abstract

The structure of the phytotoxin marticin 7a has been confirmed on the basis of 1H and 13Cmr data for the methyl ester 7c, but these and other considerations have led to a revision of the stereochemistry assignable to the isomeric isomarticin from 7b to 13. Incorporation of [1,2-13C2]- and [2-13C1]-acetates into 7a, isolated as 7c, has established a heptaketide origin for its fusarubin (1) moiety, and the tricarboxylic acid cycle as the biogenetic source of the remaining C3 fragment, only the first three turns of the cycle making significant contributions.