Studies on the biosynthesis of mould tropolones

Abstract

The mould Penicillium stipitatum Thom, first isolated from rotting wood, was described as a new species in 1935 Emmons, C.W., Mycologia 27, 128 (1935). It is characterised by the prolific formation of bright yellow ascocarps.and very scanty conidial formation. The morphological characters are well described by Raper and Thom. Raper, K.B. And C. Thom, A Manual of the Penicillia, Williams and Wilkins : Baltimore (1949). When grown as a surface culture on Czapek-Dox liquid culture medium it forms a yellow felt, and it imparts first a yellow and later a reddish brown colour to the solution, A number of pigments are responsible for this colour, the most notable of these being the closed related pair, stipitatic acid and stipitatonic acid. The first of these to be isolated was stipitatic acid, isolated in good yield by Birkinshaw et al Birkinshaw, J.H., A.R. Chambers and H. Raistrick, Biochem. J. 36, 242 (1942). from a Czapek-Dox solution on which P. stipitatum had been grown for several weeks. The chemical studies of Birkinshaw et al. showed that stipitatic acid belonged to a new class of mould metabolites. These authors were unable to formulate a structure on the basis of their extensive chemical evidence, and it remained for Dewar to do this in 1945 Dewar, M.J.S., Nature 155, 50 (1945). The relevant chemical evidence is summarised below.