Note on the conversion of the amino group of amino acids into the nitroguanidino group

A study has been made of 2‐methyl‐1‐nitroisourea as a reagent for the conversion of amino groups of amino acids into guanidino groups. This reagent has proved its usefulness in modifying the ω‐amino groups of diaminocarboxylic acids in particular. The reaction of 2‐methyl‐1‐nitroisourea with glycine, L‐ornithine and D‐ and L‐lysine to yield nitroguanidinoacetic acid, L‐nitroarginine and D‐ and L‐nitrohomoarginine, respectively, is described.