Diprenylated flavanones dorsmanine

Diprenyleriodictyol (83), the simplest diprenylated flavanone, is a citotoxic compound first reported by Harborne et al in 1993 from Vellozia coronata and V. nanuzae [66]. The structure of dorsmanine E (84) was established from analysis of the spectroscopic data for the presumed natural product as well by synthesizing it from 6, 8-diprenyleriodictyol (83) upon treatment of the latter with methanolic HC1. Dorsmanin B (85) [39] as dorspoinsettifolin (79) and 78 lack the 5-hydroxyl functionality that is common in most of the flavonoids isolated so far from Dorstenia spp and the range of compounds isolated from D. 

The results from our investigation of D. mannii indicated that this plant is a rich source of diprenylated flavanones. It is possible to speculate the biosynthesis of most of the dorsmanins 94, 86-96 from 6, 8-diprenyleriodictyol (83) which is in fact present in the plant in rather significant amount. Fig.(8) shows various epoxide intermediates arising from 83, which undergo subsequent opening by phenolic hydroxyls to yield the various diprenylated dorsmanins. 

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