Abstract: N-Benzyloxycarbonyl-L-aspartic acid (Z-Asp) is synthesized by adding benzyl chloroformate to a solution of L-aspartic acid and sodium hydroxide at relatively high temperatures of 35.degree.-55.degree. C. and over a wide pH range of 9.2-12.0 and acidifying the sodium salt product. The Z-Asp is prepared in high yields exceeding 90% and purity of better than 99% with only a minor amount of the by-product N-benzyloxycarbonyl aspartyl aspartic acid. The Z-Asp is suitable for conversion to aspartame. Carrying out the reaction at high temperatures significantly reduces cycle time while maintaining a high yield with a low dipeptide and unreacted L-aspartic acid content.