Polyketide-Terpene Hybrid Metabolites from an Endolichenic Fungus sp.

Five new polyketide-terpene hybrid metabolites (-) with highly functionalized groups, together with six known derivatives (-), were isolated from the endolichenic fungus sp. Their structures were elucidated by extensive NMR experiments including H, C, HMQC, COSY, and HMBC. The relative configurations of the new compounds were determined by analysis of coupling constants and ROESY correlations. The absolute configurations especially the secondary alcohol at C-15 in and secondary alcohol at C-14 in were established via the CD experiments of the in situ formed [Rh(OCOCF)] complex with the acetonide derivatives. These compounds were tested for their inhibition activity against six plant pathogens. Compounds and exhibited pronounced efficiency against , and compounds and potently inhibited with MIC value of 8 g/mL, which revealed the plausible ecological role of endolichenic fungus in providing chemical protection for its host lichen in the fungus-plant relationship. The biosynthetic pathway of compounds - was postulated for the first time, which paved the way for its further biosynthesis research.