No abstract

The biosynthesis of tajixanthone and related metabolites of Aspergillus variecolor has been studied by incorporation experiments with simple and advanced precursors labelled with the stable isotopes 13c, 2~ and 180. Tajixanthone is shown to be derived through ring cleavage of an octaketide-derived anthraquinone with introduction of two dimethylallyl moieties. From the results of isotopic labelling experiments and chemical studies on model compounds, an overall biosynthetic pathway is proposed and information on the mechanisms of interconversion of proposed intermediates is obtained.The isolation of tajixanthone (C25H2606) and shamixanthone (C25H2605) along with several other xanthones from cultures of Aspergillus variecolor was first reported1 in 1970. Structures (1) and (2) respectively were proposed2 for these two metabolites. However, a subsequent detailed examination of their spectral and chemical characteristics resulted in reassignment3 of the original t Dedicated to Arthur J. Birch in recognition of his contributions to the biosynthesis of natural products.

No abstract

1% and *H Labelling experiments, together with *H n.m.r. spectroscopy show that 3,5-dimethylorsellinic acid is a specific precursor of austin and terretonin in Aspergillus ustus and Aspergillus terreus, respectively, and so substantiate the mixed polyketide-terpenoid origin proposed for these metabolites from the incorporation of '3C-labelled simple precursors.

No abstract