A facile synthetic approach to prenylated flavanones: First total syntheses of (+/-)-bonannione A and (+/-)-sophoraflavanone A

A facile and efficient approach for the syntheses of both C-8 and C-6 preny lated flavonoids has been developed that features a highly regioselective p renylation of 2,4,6-trihydroxyacetophenone and regioselective cyclization o f prenylated polyhydroxy chalcones. Thus, the first efficient total synthes es of(+/-)-isophoraflavanone A (1) and (+/-)-bonannione A (2), two naturall y occurring geranylated flavanones with antibacterial activities, have been achieved starting from the key intermediate 3 via regioselective cyclizati on of geranylated tetrahydroxychalcone 4.