ISOLATION AND ELUCIDATION OF THE STRUCTURE OF HOMOCRYPTOLEPINONE

The structure of a new indolobenzazepine alkaloid, homocryptolepinone, isolated from extracts of the roots of the indigenous Ghanaian medici nal plant Cryptolepis sanguinolenta, is reported. The structure was de termined using mass spectrometric, one-dimensional nOe difference nmr, and inverse-detected two-dimensional nmr experiments which included H MQC, IDR-(Inverted Direct Response)-HMQC-TOCSY, and HMBC experiments. The structure of homocryptolepinone is significant in that it may prov ide insight into the biogenesis of the benzpyrrolizinobenzazepine port ion of the structure of the complex spiro nonacyclic alkaloid cryptosp irolepine previously isolated in these laboratories from C. sanguinole nta, and which has no precedent in alkaloid chemistry.