The condensation of pyroglutamic acids with 1,2-phenylenediamine leads to 2-(5-oxo-2-pyrrolidinyl)benzimidazoles and the cyclization of disilylated diacylhydrazines derived from the same acids gives 2-(5-oxo-2-pyrrolidinyl)-1,3,4-oxadiazoles. These compounds show weak antifungal activity.