Patent ID: 6939987

Claim:
A method for producing N-[N-[3-(3-methoxy-4-hydroxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester, comprising: subjecting N-L-α-aspartyl-L-phenylalanine 1-methyl ester and 3-(3-methoxy-4-hydroxyphenyl)propionaldehyde or a derivatives thereof to reductive alkylation in a solvent to obtain N-[N-[3-(3-methoxy-4-hydroxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester; and (2) crystallizing said N-[N-[3-(3-methoxy-4-hydroxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester wherein said reductive alkylation comprises catalytic hidrogenation, and wherein said derivative thereof is selected from the group consisting of 3-(3-methoxy-4-hydroxyphenyl)-2-propenylaldehyde 3-(3-methoxy-4-protected-hydroxyphenyl)propionaldehyde, 3-(3-methoxy-4-protected-hydroxyphenyl)-2-propenylaldehyde, and acetals derived therefrom.