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 prenylated flavonoids has been developed that features a highly regioselective prenylation of 2,4,6-trihydroxyacetophenone and regioselective cyclization of prenylated polyhydroxy chalcones. Thus, the first efficient total syntheses of (+/-)-sophoraflavanone A (1) and (+/-)-bonannione A (2), two naturally occurring geranylated flavanones with antibacterial activities, have been achieved starting from the key intermediate 3 via regioselective cyclization of geranylated tetrahydroxychalcone 4.