Synthetic modulation of the peripheral 2-, 3-, 9- and 12-oxygenation pattern of rotenoids

Abstract

Synthetic modulations of the rotenoid munduserone, in terms of the peripheral oxygenation pattern, have been carried out for structure–activity purposes. Synthesis by propargyl Claisen rearrangement was successful in cases having 2,3-dimethoxylation in ring A (as in natural Leguminous rotenoids), but failed when this electron release was not present. Attempts to catalyse an unsuccessful case led instead to an alkylidenedihydrobenzofuranone. The rotenoid lacking 2,3-dimethoxylation was made by chromanone β-ester synthesis, as was the parent rotenoid of the Boerhaavia(monocotyledonous) group.

The rotenoid 12-carbonyl can be removed by reduction and dehydration, and the resulting stilbene, when catalytically hydrogenated, gives the cis-B/C-12-deoxy compound. When the reduction is effected by dissolving magnesium in methanol a separable mixture of cis- and trans-12-deoxyrotenoids is obtained.