UNUSUAL POLYKETIDES FROM THE WOOD-DECAY FUNGUS SISTOTREMA RADULOIDES

The metabolites of the wood rot decay fungus Sistotrema raduloides (P Karst) Donk have been investigated and a new type of norpentaketide ha s been discovered. The compounds sistodiolynne (1), sistolynone (5), a nd sistopyrone (6) represent new carbon skeletons among natural produc ts. The compounds are very unstable and readily polymerize in the pres ence of air to give black insoluble material. It has been shown by C-1 3 NMR labelling experiments that they arise from five acetate units, a nd that a methyl carbon of one of the acetate units is lost during the biosynthesis. The structures were determined by spectroscopy methods, mainly NMR, and the absolute configuration of sistodiolynne was estab lished by circular dichroism methods.