Not less than-95.0%
((S)-1-Ethoxy-1-oxopentan-2-yl)-L-alanine;(S)-N-(1-Carboxyethyl)-L-norvaline 1-Ethyl Ester; N-((S)-Ethoxycarbonyl-1-butyl)-(S)-alanine; (S)-2-(((S)-1-Ethoxy-1-oxopentan-2-yl)amino)propanoic Acid