THE SYNTHESIS, STRUCTURE, AND ANTICANCER ACTIVITY OF CIS-4',7-DIHYDROXYISOFLAVAN-4-OLS AND TRANS-4',7-DIHYDROXYISOFLAVAN-4-OLS

cis-4',7-Dihydroxyisoflavan-4-ol (4) and trans-4',7-dihydroxyisoflavan -4-ol (5), two proposed metabolites of daidzein (4',7-dihydroxyisoflav one), have been synthesized and fully characterized for the first time . The vicinal coupling constants of the pyran ring protons are compati ble with a half-chair conformation. The cis isomer is anancomeric whil e the trans isomer consists of a 68:32 mixture of two ring inversion c onformers. Molecular mechanical calculations are in agreement with the half-chair conformation of the pyran ring and suggest that the cis is omer is biased because of an unfavorable gauche interaction of the equ atorial hydroxyl and the axial phenyl group. The isoflavanols 4 and 5 are comparable to genistein (4',5,7-trihydroxyisoflavone) in antitumor activity against human prostate cancer cells.