Abstract:
Puberulic and puberulonic acids were isolated together as metabolites of certain penicillia by Birkinshaw and Raistrick Birkinshaw, J.H., and Raistrick, H.: Biochem. J. 26, 441 (1932) in 1932. A limited chemical investigation of the former acid was undertaken, both by these workers and by Barger and Dorrer Barger, G, and Dorrer, O.: Biochem. J. 28, 11 (1934.), but it was not found possible at that time to advance a reasonable structure for either acid.
A similar problem followed the isolation in 1942 Birkinshaw, J.H., Chambers, A.R. and Raistrick, H.: Biochem. J. 36, 242 (1942) of another penicillium metabolite, stipitatic acid. Despite a fairly detailed investigation the results could not inmediately be correlated with a suitable structure. In 1945 came Dewar's novel suggestion Dewar, M.J.S.: Nature 155,50 (1945) of a seven membered aromatic ring, designated by him "tropolone", which seemed to provide an explanation for the observed chemistry of stipitatic acid. According to this hypothesis, stipitatic acid could be assigned the structure I, and the parent canpound II, IIa, would represent a new type of ring system.
