BIOSYNTHESIS OF BREVIANAMIDE-A AND BREVIANAMIDE-B - IN SEARCH OF THE BIOSYNTHETIC DIELS-ALDER CONSTRUCTION

A [C-13]labeled hypothetical intermediate metabolite that was invoked by Birch in the biogenesis of brevianamides A and B has been synthesized and used in a biosynthetic feeding experiment. No incorporation of this substance was evident nor could it be detected in culture extracts of the producing organism Penicillium brevicompactum. In contrast with this, [H-3]labeled deoxybrevianamide E was shown to be efficiently incorporated in brevianamides A, B, and E, while [H-3]labeled brevianamide E was not incorporated at all in these substances. Moreover, brevianamide E has been found not to be an artifact, in contrast with an earlier suggestion found in the literature. These results are discussed in terms of an alternative biosynthetic pathway for the brevianamides.