Studies on Metabolites of Macrophoma commelinae. III. : Isolation of New Metabolites and Biosynthesis of Macommelin Group

Three new metabolites, named macommelinal, macrophin and macrophic acid, were isolated from the culture broth of Macrophoma commelinae IFO 9570. Their structures were determined to be 2-(4-methoxy-6-methyl-2-oxo-2H-pyran-5-yl)ethanal, 3-methyl-2-butenoic acid (E)-[5-hydroxymethyl-4-methoxy-6-(2-methoxycarbonylethenyl)-2-oxo-2H-pyran-3-ly]methyl ester and 3-(4-methoxy-3, 5-dimethyl-2-oxo-2H-pyran-6-yl)-2-propenoic acid, respectively. 4 Acetyl-3-methoxy-5-methylbenzoic acid, now named macrophomic acid, was also isolated from a large-scale culture.The biosynthesis of the macommelin group, novel 5-substituted 2-pyrone metabolites, has been investigated by feeding experiments with [1-13C]-, [1, 2-13C2]- and [1-13C, 2-2H3]acetate and [2-13C]malonate. It was concluded that all these metabolites originated from a single straight tetraketide chain. Furthermore, the biogenetic mutual relationships of these metabolites including potential intermediates were estabished through incorporation experiments with 14C-labeled compounds.