Further Dihydrochalcones from Crotolaria ramosissima

Crotolaria ramosissima is a weed plant belonging to the family Leguminoseae. It is a much branched sticky woody herb. The flowers are yellow tinged with purple. It is distributed in some places of Tamilnadu and coastal areas of Andrha Pradesh. The plant contains waxes, and, when flowering, a yellow exudate appears in the inflorescences. Recently, we published the corrected structure of crotaramosmin (1) from crotolaria ramosissima which appeared to be a dihydrochalcone, a class of compound which is rare as a plant secondary metabolite. Except 1, only one other instance of a dihydrochalcone possessing a chromenyl moiety has been reported in the literature. This is a synthetic compound and has an unsubstituted phenyl ring (see Scheme 1: X = Y = H). Our continued interest on crotolaria ramosissima led to the identification of two more dihydrochalcones, crotaramin (2) and crotin (3) (Scheme 1).