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The structures of shamixanthone and tajixanthone, optically active metabolites of Aspergillus variecolor, are shown [3,2-a]xanthen-l2one (V) respectively. These structures were established by detailed analyses of the ' H and lSC n.m.r. spectra of the metabolites and their derived compounds as well as by chemical degradation of the substituted dihydrobenzopyran system. The absolute configurations were assigned by application of the Horeau asymmetric synthesis.

Incorporations of diethyl [l -14C]rnalonate by Monascus purpureus Wentii into rubropunctatin (111; R = C5Hll) and monascorubrin (111; R = C7HI5) have shown that the main poly-(3-ketide chain of these metabolites IS assembled from acetate plus malonate in the normal way. However, the p-0x0-lactone systems are derived by condensation of hexanoate and octanoate, respectively, with acetate. Although malonate is utilised in the normal way in the derivation of these fatty acid equivalents, it is not involved in the conversion of these into p-oxodecanoate and p-0x0-octanoate equivalents, respectively. A probable explanation of these results is suggested. Liver pool IKCORPORATION of sodium [1-14C] acetate and [14C]formate into the fungal metabolites sclerotiorin (I),2 rotiorin (11),3 rubropunctatin (111; R = CSH,~),~ and monascin (IV) 3 have shown distributions of label compatible with the patterns (1)-(IV), (a = radioactivity from [1-14C]acetate, = = radioactivity from the C, pool, contributed by [14C]formate), indicating that these compounds are biogenetically derived on polyp-ltetide pathways. Structural analysis suggests that in each of these compounds two chains must be present, the principal one forming the main chromophores and the second one increasing in complexity from 0-acetate (in 1) to an acetoacetyl which has undergone ring closure, giving the p-0x0-lactone system (in 11), and

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