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).