Total synthesis of two isoflavone C-glycosides:: genistein and orobol 8-C-β-D-glucopyrano sides

Genistein and orobol 8-C-beta-D-glucopyranosides (1 and 3) were firstly synthesized in overall yields of 39% and 41% from 2,4-di-O-benzylphloroacetophenone (4), as follows: (1) the formation of the chalcone (6, 7) by aldol condensation of the benzyl-protected C-glycosylphloroacetophenone (5), a key intermediate of the total synthesis of I and 3 and synthesized by a C-glycosylation method involving the O -> C glycoside rearrangement of 4 in 96% yield; (2) the formation of isoflavones (10, 11 and 12, 13) by the formation of acetals by oxidative rearrangement of the protected chalcones (8 and 9) using TI(NO3)(3), followed by acid-catalyzed cyclization: (3) a final debenzylation by hydrogenolysis. (c) 2006 Elsevier Ltd. All rights reserved.