Traegeric Acid and Other Metabolites of Aspergillus flaschentraegeri

The remarkable transformation of the antifungal antibiotic traegeric acid, by means of copper sulphate in ethereal sulphuric acid, has been elucidated by inter-relation with the new norditerpene pigment flascherone, which is also produced by Aspergillus flaschentraegeri. This has allowed the structure of the antibiotic to be elaborated as an unusual diterpene pseudo-acid. Esterification of the antibiotic led to a variety of products depending on the conditions. Formation of one product obtained with diazomethane was shown to involve attack at the enone system to give a cyclopropyl ketone grouping. Varied chemical transformations of this compound, including reductive studies and ozonolysis have established the relative configuration at 2 of the asymmetric centres, and afforded evidence concerning the remaining centres. Routes to heavy atom and mono-carbonyl derivatives for X-ray and ORD work, respectively, have been investigated. The known anthraquinone physcion and a related pigment have been isolated from the fungus. The demonstration of nuclear overhauser effects in the n. m. r. spectrum of the latter has played a part in establishing its structure as the first C-prenylated anthraquinone. A phthalic acid metabolite has been characterised and synthetic studies on it carried out