Efficient Stereo-Selective Fluorination on Vitamin D 3 Side-Chain Using Electrophilic Fluorination.

Our research regarding side-chain fluorinated vitamin D 3 analogues has explored a series of efficient fluorination methods. In this study, a new electrophilic stereo-selective fluorination methodology at C24 and C22 positions of the vitamin D 3 side-chain was developed using N -fluorobenzenesulfonimide (NFSI) and CD-ring imides with an Evans chiral auxiliary ( 26 , 27 , 30 ).