Rhamnofolanes and Daphnanes

Rhamnofolanes such as (-)-20-acetoxy-9-hydroxy-l,6,14-rhamnofolatriene-3,13-dione from Croton rhamnifolius (Euphorbiaceae) and other constituents from various Jatropha species rarely occur in plants. 

Daphnanes are more frequently found such as daphnetoxin in flowers and bark of Daphne species exemplified by Daphne mezereum (Thymeliaceae), irritating human skin and mucous membranes, as well as (+)-resiniferatoxin from Euphorbia resinifera and related species. Some daphnanes are reported to have antineoplastic and antileukemic activities. 

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Lathyrane formally cyclizes to tigliane by closing the C-5-C-14-bond which, on its part, converts into rhamnofolane and daphnane by opening the 2,15- and the 1,15-bond, respectively (Table 4). Eunicellanes represent 2,5-cyclocembranes, which formally undergo C-18-methyl shift from C-4- to C-3 resulting in the formation of asbestinanes. Briaranes are 3,8-cyclocembranes (Table 4). 

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