Synthesis of L-4,4-difluoroglutamic acid via electrophilic difluorination of a lactam.

[formula: see text] An enantiomerically pure bicyclic lactam proved to be an excellent substrate for electrophilic difluorination using N-fluorobenzenesulfonimide. The resulting difluorinated lactam can be easily converted into L-4,4-difluoroglutamic acid. To the best of our knowledge, this is the first example of a synthetically useful electrophilic difluorination of an unactivated lactam.