| Abstract: | The structure of a new indolobenzazepine alkaloid, homocryptolepinone, isolated from extracts of the roots of the indigenous Ghanaian medicinal plant Cryptolepis sanguinolenta, is reported. The structure was determined using mass spectrometric, one-dimensional nOe difference nmr, and inverse-detected two-dimensional nmr experiments which included HMQC, IDR-(Inverted Direct Response)-HMQC-TOCSY, and HMBC experiments. The structure of homocryptolepinone is significant in that it may provide insight into the biogenesis of the benzpyrrolizinobenzazepine portion of the structure of the complex spiro nona-cyclic alkaloid cryptospirolepine previously isolated in these laboratories from C. sanguinolenta, and which has no precedent in alkaloid chemistry. |
