The Structural Revision and Total Synthesis of Carambolaflavone A.

The synthesis of both enantiomers of carambolaflavone A, the antidiabetic and flavonoid C-glycoside, was achieved for the first time via a 12-longest-linear-step with 16% (l-fucose) and 11% (d-fucose) overall yields. Through the synthetic investigation, the adverse effect of 4A MS in Suzuki C-glycosylation was disclosed, the mechanism of hydrogen-bonded-phenol involved Suzuki C-glycosylation was clarified, and the authentic structure of carambolaflavone A was also determined.