In order to examine their oral progestational activity, some 17α-acyloxy-3, 5-pregnadien-20-one derivatives (IIIa, IIIb, IIIc, IIId, IIIe, VI, VII, VIII, and IX) were synthesized. III, VI, and VII were obtained by dehydration of 4-en-3-ol derivatives, which were obtained by selective reduction of 17α-acyloxyprogesterone derivatives with sodium borohydride, in the presence of phosphomolybdic acid in acetone solution at room temperature or boiling temperature. VIII and IX were obtained by the reaction of 17α-acyloxyprogesterone derivatives with acetyl chloride at room temperature. The effect of substituents in 3, 5-diene derivatives on the oral progestational activity was discussed.