Various allenenols lactones [5(E)-(2-allenylidene)-tetrahydro-2-furanones] have been synthesized by reacting 4-pentynoic acid and 2-alkynyl acetate in dimethyl sulfoxide in the presence of K2CO3, Pd(OAc)2 as the catalyst and tri(2-furyl) phosphine as the ligand. The biological activity of these compounds as protease inhibitors has been proven.