Patent ID: 6914151

Claim:
A method for preparing A-type crystals of N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine methyl ester, comprising: crystallizing N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine methyl ester from a solution comprising N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine methyl ester and a solvent, to obtain A-type crystals of N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine methyl ester, wherein said solvent is selected from the group consisting of water and mixtures of water and a lower alcohol, wherein said crystallizing is carried out such that the temperature of said solution is maintained above 47° C. until onset of nucleation of said A-type N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine methyl ester.