In continued cooperation with Prof. J.M. Cook and his coworkers at the University of Wisconsin-Milwaukee, the synthesis of di- and polycyclic ring systems composed of fused cyclopentane rings has been developed further. The approach chosen is based on the ready stereospecific formation of derivatives of cis-bicyclo(3.3.0) octane-3,7-dione (1) from 1,2-dicarbonyl compounds and esters of 3-oxoglutaric acid (the """"""""Weiss reaction""""""""). In 1986, the first synthetic derivative of a particular tetracyclic system has been obtained using this approach. One compound derived from this system has been encountered as a transformation product of a natural terpenoid, but no previous synthetic work in this series seems recorded. The synthesis required solution of two non-trivial problems: (1) modification of only one of the two chemically identical carbonyls in an intermediate of type (1), achieved by selective monoketalization with a bulky diol, and (2) prevention of an undesirable 1,2- migration of a double bond during a Wolff-Kishner reduction by addition of silver carbonate. A review of the chemistry of natural perylenequinones, written by U. Weiss, L. Merlini, and G. Nasini, has been completed and is in press. It is the first comprehensive review of this class of substances, which includes many powerful photosensitizers.
