Synthetic preparation of N-methyl-α-amino acids

An overview is given of the methods for the synthesis of N-methylamino acids (NMAs) and some of the synthetically challenging aspects of N-methylation including region-specific methylation, mono-N-methylation, and development of racemization free chemistry. The synthethic methods reviewed reveal the difficulty that chemists have had in incorporating a single methyl group at the α-amino position and the problems encountered in applying these methods to the common 20 naturally occurring L-amino acids.