New Synthetic Routes to Biologically Interesting Geranylated Flavanones and Geranylated Chalcones: First Total Synthesis of (±)-Prostratol F, Xanthoangelol, and (±)-Lespeol

A new and efficient synthetic approach to biologically interesting geranylated flavanones and geranylated chalcones is described. Thus, the first total syntheses of the geranylated flavanones (+/-)-prostratol F (1), (+/-)-8-geranyl-3',4',7-trihydroxyflavanone (2), and (+/-)-6-geranyl-5,7-dihydroxy-3',4'-dimethoxyflavanone (3) were carried out starting from 2,4-dihydroxyacetophenone (10) and 2,4,6-trihydroxyacethophenone (17) in five to six steps (Schemes 2 and 3). The geranylated chalcones xanthoangelol (4), 3-geranyl-2,3',4,4'-tetrahydroxychalcone (5), (+/-)-lespeol (6), and lespeol derivatives (+/-)-7-9 were synthesized starting from 2,4-dihydroxyacetophenone (10) in three to four steps (Schemes 2 and 6).