Antifertility activity of N-protected glycine activated esters

A series of N-protected glycine activated esters was found to have antifertility activity in mice when administered intravaginally. The N-carbobenzoxyglycine vinyl ester and N-carbobenzoxyglycine 1,2-dibromoethyl ester analogs possessed the best activity in inhibiting pregnancy but were much less active when administered intraperitoneally. The acrosin enzymatic activity of sperm also was inhibited by these N-protected glycine activated esters, as measured by N-alpha-benzoyl-L-arginine ethyl ester and azocasein hydrolysis. The ability to inhibit N-alpha-benzoyl-L-arginine ethyl ester hydrolysis, a trypsin-like activity, appeared to have a positive correlation with antifertility activity when the agents were administered intravaginally.