The synthesis of O-ethyl-DL-homoserine (V) was achieved by the condensation of β- ethoxyethylbromide (II) with diethyl acetoaminomalonate (III) and by the successive hydrolysis of diethyl ethoxyethylacetoaminomalonate (IV) with hydrochloric acid. The optical resolution of O-ethylhomoserine was performed enzymatically using papain. The O-ethyl-L- homoserine (VIII) obtained by the resolution was shown to be identical with the amino acid ...