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Pure Appl. Chem., 2004, Vol. 76, No. 5, pp. 1025-1032

Synthesis of naturally occurring o-heterocyclic compounds of biological activity

Sándor Antus, Katalin Gulácsi, László Juhász, Loránd Kiss and Tibor Kurtán

Department of Organic Chemistry, University of Debrecen, H-4010 Debrecen, P.O. Box 20, Hungary

Abstract: The total synthesis of (−)-cabenegrin A-I was achieved via (−)-6aR,11aR maackiain, which was obtained by optical resolution of racemic maackiain using S-(−)-alpha-methylbenzyl isocyanate. The synthesis of rac-maackiain was performed both with the Heck oxyarylation of 7-benzyloxy-2H-chromene and the BF3OEt2 mediated ring closure of isoflavan-4-ol derivatives, the latter of which provided much higher yields. The first enantioselective synthesis of trans-6aS,11aR-pterocarpan and its conversion to cis-6aS,11aS -ptarocarpan was also presented starting from racemic 2'-benzyloxyflavanone. Their stereochemistry was deduced by circular dichroism (CD) as well as by X-ray analysis of the ketal intermediate.