Isolation and structure of the metabolites from diplodia maydis

Abstract

Investigation of toxic extracts from cultures of the fungus Diplodia maydis (Berk.) Sacc. [ synonyms D. zeae (Schw.) Lev. and Stenocarpella maydis (Berk.)] led to the isolation of diplodiatoxin, a known metabolite, as well as four new metabolites viz. 3-hydroxydiplodiatoxin stenocarpin, steno-carpin 6-0-(4-0-methyl-orsellinate) and carpellin. The structure elucidation of the new compounds is based on a detailed analysis of their highfield 1H and 13 c nuclear magnetic resonance spectra. The relative configurations were deduced from the magnitude of the proton-proton coupling constants and the results obtained from homonuclear proton-proton nuclear Overhauser effect (n.O.e.) studies. The absolute configuration of stenocarpin 6 - 0- ( 4 - 0-methylorsellina te) was determined by the 'partial resolution' method of Horeau. The biosynthetic pathway leading to d±plodiatoxin was investigated by incorporation studies with 13 c-, 2 H and 18 0-labelled precursors.