Biosynthesis of LL-D253α, a polyketide chromanone metabolite of Phoma pigmentivora: incorporation of 13C, 2H and 18O labelled precursors

Abstract

The incorporation of ¹³C, ²H and ¹⁸O labelled acetates and ¹⁸O₂ gas into LL-D253α, a chromanone metabolite of Phoma pigmentivora and other fungi, and analysis of the enriched metabolites by ¹³C and ²H NMR spectroscopy and mass spectrometry indicates its formation via two preformed polyketide chains. Evidence is presented for the mechanism of formation of the chromanone ring and a cyclopropyl intermediate is proposed to account for the unexpected randomisation of label observed in the hydroxyethyl side chain. A pathway is proposed to explain the occurrence of the co-metabolites LL-D253β and γ.