12.7 The Synthesis of α-Amino Acids
Some of the common methods employed for the synthesis of α-amino acids follow:

12.7.1 From α-Halo acids

The simplest method is the conversion of carboxylic acid into it’s α-bromo-derivative that can be reacted with ammonia to give α-amino acid (Scheme 10).

Scheme 10

Hell-Volhard-Zelinski reaction is generally used to prepare α-bromo acid (Scheme 11). The treatment of the acid with bromine in the presence of a small amount of phosphorus gives acid bromide which undergoes (electrophilic) bromination at the α-position via its enol tautomer. The resulting product exchanges with more of the acid to give α-bromo acid together with more acid bromide for the further bromination.