Fungal Terpenoids

Studies of the terpenoid constituents of the fungus Penicillium brevicompactum have established the presence of two new compounds (a furan and a dihydrofuran) with the same nucleus as mycophenolic acid but with modified terpenoid side chains. Elucidation of the structure of these has been assisted by various transformations involving the side chain. The structure of mycochromenic acid,a further compound of this type which was previously isolated from P. brevicompactum has been confirmed by a synthesis which establishes a new route to chromenes. From the same fungus three related sesquiterpene benzoates (pebrolide ,deoxypebrolide and desacetylpebrolide) were isolated and their structures elucidated by chemical studies and by an X-ray analysis of bromoacetylpebrolide. NMR studies of pebrolide and its derivatives and the X-ray data showed that the preferred conformation in solution and the conformation in the crystal are very similar. A sequence for degradation of biosynthetically labelled pebrolide was established. This was applied to material derived from doubly labelled 214C/23H mevalonate and the presence of label at C-l and at the 4alpha carbon established