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The isolation of lapidosin (1) from Penicillium lapidosum and of diversonol (4) from P. diversurn is described and possible biosynthetic origins are suggested.

The structures of cytochalasins C and D, metabolites of Metarrhizium anisopliae, have been determined.THE cytochalasins 1 are a new class of mould metabolite which produce unique effects on mammalian cells.2Cytochalasins A and By produced by Helminthosporium dematioideum, have been shown 1,3 to have structures (Ia) and (Ib) respectively (cytochalasin B is identical with phomin, a metabolite of a Phoma sp?), and the isolation of cytochalasins C and D from Metarr?zizium anisopZiae has been briefly reported.1 t We report here experiments which lead us to propose structures (IIa) and (111) for cytochalasins C and D respectively. The compounds are produced in rather low yield and are difficult to separate. In particular, it is difficult to obtain cytochalasin D, which is the minor product, free from cytochalasin C; for this reason, most of the degradative experiments have been carried out with cytochalasin C.Cytochalasins C and D are isomers C,H3,N0,. The nature of the isomerism and of a large part of the molecules is revealed most clearly by consideration of the properties of the isomeric carboxylic acids, C,H,,NO,, obtained by alkaline hydrolysis of the mould metabolites. The n.m.r. spectrum (Table ) of the product (IV) from cytochalasin C shows signals due to a phenyl ring, a tram-disubstituted double bond, a secondary hydroxygroup, two allylic methyl groups, a secondary methyl t Note added in proof: It is clear from its published i.r. spectrum that the recently isolated antibiotic zygosporin (S.

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