Aspartame precursor synthesis in water miscible cosolvent catalysed by thermolysin

Summary The synthesis of the dipeptideN-benzyloxycarbonyl-L- aspartyl-phenylalanine methyl ester, aspartame precursor, catalysed by thermolysin in aqueous and aqueous methanolic solutions was studied. Thermolysin with concentration as low as 10 M in 25% methanol can catalyse the synthetic reaction. The optimum methanol compositions at 4°C and 37°C were 50% and 25% respectively where an increase in peptide yield of 85% was obtained for both conditions as compared to that in water.Abbreviations N-cbz-L-Asp N-benzyloxycarbonyl-L-aspartic acid - L-Phe-OMe L-phenylalanine methyl ester - N-cbz-L-Asp-Phe-OMe N-benzyloxycarbonyl-L-aspartyl-phenylalanine methyl ester All the % of methanol is a volume % in water unless otherwise specified.