Diprenylated flavanones

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. 

Rao et al. revised the structure of crotaramosmin (286), formerly described as a prenyl-flavanone, to 2, 4-dihydroxy-6",6"-dimethylpyrano[2",3" 4, 3 ]dihydrochalcone. Two derivatives of crotaramosmin, crotaramin (287) and crotin (292), were later isolated from the same source, Crotalaria ramosissima (cited incorrectly as Crotolaria ramosissima) Kanzo-nol Y (294) is an uncommon diprenylated a-hydroxydihydrochalcone found in cultivated licorice (Glycyrrhiza glabraf for which the absolute configuration was determined by... 

The major types of bioactive constituents reported from Broussonetia papyrifera are the prenylated flavonoids, which include compounds of the diphenylpropane, chalcone, flavan, flavanone, flavone, flavonol, and aurone classes (Table 2), Fig. (7). An early study on B. papyrifera resulted in the isolation of two diphenylpropanes, broussonins A (29) and B (30), and a coumarin, marmesin (52), with antifungal activity [39]. Also, a diprenylated diphenylpropane derivative, kazinol F (31) [40], was reported as an antioxidant and tyrosinase inhibitory constituent [34]. 

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