Fast and convenient synthesis of α-N-protected amino acid hydrazides

A fast, simple and convenient synthesis of α-N-protected amino acid hydrazides is reported. The procedure involves the reaction between hydrazine monohydrate and the mixed anhydride obtained from an α-N-protected amino acid and ethyl chloroformate. When methylhydrazine was used, the reaction showed a good selectivity, yielding a mixture of 1-acyl-1-methylhydrazine and 1-acyl-2-methylhydrazine in a ratio 87:13. In contrast, when the reaction was carried out with phenylhydrazine, only 1-acyl-2-phenylhydrazine was obtained. No significant difference in reactivity was observed with the different amino acids and N-protection introduced.