Biosynthesis of LL-D253? in Phoma pigmentivora. Incorporation of 13C, 2H, and 18O enriched precursors

The incorporation of 13C, 2H, and 18O labelled acetates and 18O2 gas into LL-D253α(1), a chromanone metabolite of Phoma pigmentivora, and analyses of the enriched metabolites by 13C and 2H n.m.r. and mass spectroscopy indicate its formation from two preformed polyketide chains; evidence for the mechanism of formation of the chromanone ring is presented, and a cyclopropyl intermediate is proposed to account to account for the unique randomisation of label observed in the hydroxyethyl side chain.