To develop more potential angiotensin converting enzyme (ACE) inhibitors, a series of captopril (Cap) derivatives were synthesized, including Cap-glycine methyl ester, Cap-l-alanine methyl ester, Cap-l-aspartic acid dimethyl ester, Cap-l-lysine methyl ester, Cap-O-acylisourea, acetyl captopril, and benzoyl captopril. The resulting products were characterized by IR and UV–visible spectroscopy and MS, which showed the desired products were successfully synthesized. This could serve as a guide for rational design of highly potent ACE inhibitors.