(R)-2-Aminobutanoic Acid Methyl Ester Hydrochloride is used as a reagent in the synthesis of pteridine derivatives which have antibacterial and antifungal activies. (R)-2-Aminobutanoic Acid Methyl Ester Hydrochloride is also used in the synthesis of diazepanones as dipeptidyl peptidase IV inhibitors.