Two cyclopentapeptides cyclo(ProTyrLeuAlaGly)(1) and cyclo(AlaTyrLeuAlaGly)(2) isolated and identified from a Chinese medicinal herb were chosen as model cyclopeptides to evaluate a novel coupling reagent DEPBT (3-(diethoxy-phosphoryloxy-1,2,3-benzotriazin-4(3H)-one). DEPBT was used for synthesis of cyclic peptides in one-pot procedure. Compared with some other coupling reagents, the cyclization yields were satisfactory.