4.6.1.1 From α-Halo acids

The simplest method consists of the conversion of carboxylic acid into it's α -bromo-derivative which could be reacted with ammonia to give α -amino acid.

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

The amino group may also be introduced by Gabriel procedure (4.2.2) which gives better yield compared to that of the above described reaction with ammonia as an aminating agent.

The amino group can also be introduced via nitrosation (4.5.1) followed by reduction and hydrolysis processes.