Syntheses of N-Alkyl-aspartic Acids and N²-Alkyl-α-asparagines

General methods for the preparation of N-alkyl-aspartic acids and N²-alkyl-α-asparagines via maleic anhydride were worked out. The former were obtained on alkaline hydrolysis of their β-methyl esters, obtained by addition of amines to monomethyl maleate. Reaction of ammonia with the anhydride hydrochlorides of N-alkyl-aspartic acids or with their mixed anhydrides with chloroformic acid (obtained on reaction with phosgene) gave N²-alkyl-α-asparagines.