Synthesis and Biosynthesis of Pulvinic Acid Derivatives

In the cases of xerocomic acid and gomphidic acid the classical route afforded mixtures of the natural pigments and their regioisomers. Edwards and Gill 202) were able to separate the mixture of (72) and (84) obtained from the dilactone (100) by fractional crystallisation. Interestingly, when the mixture of (72) and (84) was heated with hy-droiodic acid in acetic acid for longer than one hour exclusive formation of xerocomic acid (72) was observed. 

Symmetrically substituted pulvinic dilactones are conveniently obtained from terphenylquinones by oxidative ring cleavage. This may be brought about with hydrogen peroxide 425), with lead tetra-acetate 248) or best with dimethyl sulphoxide and acetic anhydride 493, 715). Because of the ease with which terphenylquinones themselves may be derived by methoxide catalysed rearrangement of grevilhns 462) 

Xerocomic acid exhibits moderate antibiotic activity against several bacteria 533, but compare 76). In recent years numerous pulvinic acid derivatives have been synthesised, and many have been shown to possess useful anti-inflammatory properties 710). 

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