Enantioselective fluorination mediated by N-fluoroammonium salts of cinchona alkaloids:: First enantioselective synthesis of BMS-204352 (MaxiPost)

We have employed a cinchona alkaloid/Select-fluor-mediated enantioselective fluorination of the oxindole 2 to achieve the first enantioslective synthesis of BMS-204352 (MaxiPost, S-1), an effective opener of maxi-K channels. Fluorination occurred to produce S-1 with 84% ee using the bis-cinchona alkaloid (DHQ)(2)AQN. Recrystallization produced enantiomerically pure (>99% ee) product. Quinidine-mediated fluorination of 2 gave the (R)-antipode of 1 with 68% ee.