Harzianone Biosynthesis by the Biocontrol Fungus Trichoderma.

Analysis of the volatile terpenes produced by seven fungal strains of the genus Trichoderma by use of a closed-loop stripping apparatus (CLSA) revealed a common production of harzianone, a bioactive, structurally unique diterpenoid consisting of a fused tetracyclic 4,7,5,6-membered ring system. The terpene cyclization mechanism was studied by feeding experiments using selectively 13 C- and 2 H-labeled synthetic mevalonolactone isotopologues, followed by analysis of the incorporation patterns by 13 C NMR spectroscopy and GC/MS. The structure of harzianone was further supported from a 13 C,13 C COSY experiment of the in-vivo-generated fully 13 C-labeled diterpene.