Some new unsymmetrical and optically active 2,5-disubstituted 1,3,4-oxadiazoles 5a-j were efficiently synthesized by cyclization reaction of diacylhydrazides 4a-j. The synthesis of the title compounds was achieved by the reaction of acyl hydrazides 3a-b and N-phetaloyl-L-amino acids 1a-e in the presence of the phosphoroxy chloride (POCl(3)) as an anhydrous reagent.