Two new indoloquinoline alkaloids from Cryptolepis sanguinolenta: Cryptosanguinolentine and cryptotackieine

The roots of the indigenous West African shrub Cryptolepis sanguinolenta have proved to be a rich source of indoloquinoline alkaloids. To date, all of the alkaloids isolated have been analogs of indolo[3,2-b]quinoline. We now wish to report examples of two new indoloquinoline alkaloids which differ in the fusion of the indole and quinoline rings. The first, cryptosanguinolentine, is an angular indolo[3,2-c]quinoline. The second, cryptotackieine, is a linear indolo[2,3-b]quinoline system. Both of these families of alkaloids are without precedent from C. sanguinolenta. The structures of both were established through the extensive use of inverse-detected micro nmr methods.