Rapid access to N-Boc phenylglycine derivatives via benzylic lithiation reactions

We report a novel and efficient method for the enantioselective synthesis of N-Boc protected phenylglycines. Yields and enantiomeric ratios vary widely depending on the nature of the solvent, the substrate and on the method of forming the chiral complex. Results show that the major reaction pathway is an enantioselective deprotonation/substitution process. The enantioselectivity appears to be limited by the chiral discrimination ability of the s-BuLi–(−)-sparteine complex. The synthetic method described is one of the shortest route to useful enantioenriched N-Boc phenylglycine derivatives.