Cryptospirolepine, a unique spiro-nonacyclic alkaloid isolated from cryptolepis sanguinolenta

From the alkaloidal fractions of the West African plant Cryptolepis sanguinolenta (Asclepiadaceae), two alkaloids were purified: one was identified as the known in-doloquinoline alkaloid cryptolepine [1]. A second, novel alkaloid was shown to have an empirical formula of C34H24N4O based on exact mass measurement. Through the concerted application of a series of homonuclear and inverse-detected 2D nmr experiments, the structure of the second alkaloid was established as a spiro-nonacyclic alkaloid, cryptospirolepine. One portion of the structure of cryptospirolepine [2] may be biogenetically derived from cryptolepine [1]. © 1993, American Chemical Society. All rights reserved.