Natural acetylenes. Part XX. Tetra-acetylenic and other metabolites from Fistulina hepatica(Huds) Fr.
The isolation, characterisation and structure determination of five polyacetylenes from Fistulina hepatica are described. They include two C13-tetra-acetylenic compounds which, in addition to adding a new chromophore to those of the fungal metabolites, also represent the first hydrocarbon (I) and the first tetra-ol (V) to be encountered. The structure and stereochemistry of the tetra-ol (V) followed from two experiments; firstly, periodate oxidation gave deca-2,4,6,8-tetraynal and secondly, base-catalysed cyclisation to the triyn-enol ether (VII) followed by ozonolysis, gave (–)-lyxonic acid lactone (VIII). The C13-triynene alcohol (II) is also a new metabolite. The remaining two metabolites characterised, were cis- and trans-dehydromatricarianol (III and IV), the former a new natural product, whereas the latter ranks as the most widespread fungal polyacetylene.