Resibufogenin (IX), which is 14β, 15β-epoxy compound in bufadienolides, occurs in nature, but the corresponding 14α, 15α-epoxy compound is unknown. In order to examine the ring-opening reaction of 14, 15-epoxy function with hydroiodic acid, 14α, 15α-epoxy-3β-hydroxy-5β-bufa-20, 22-dienolide (VI) and its 3-acetate (VII) were synthesized (Chart 1). Reaction of 14β, 15β-epoxy compound (IX) or 14α, 15α-epoxy compound (VI) with hydroiodic acid gave Δ14-anhydrobufalin (II), which was a normal reduced product, 14α-artebufogenin (XI), and 14β-artebufogenin (XIII), respectively. A similar reaction of two acetates (X or VII) gave the corresponding acetates, IV, XII and XIV, respectively (Chart 2). The formation of 14α- and 14β-artebufogenin indicates that the acid-catalyzed ring-opening reaction occurred at a time. Based on these results, reaction of 5, 6-epoxy function was reexamined. As was excepted, reaction of 5β, 6β-epoxy compound (XV) or 5α, 6α-epoxy compound (XVI) afforded 3β-acetoxy-5, 6β-dihydroxy-5α-cholestane (XIX), besides cholesteryl acetate (XVII) and cholesterol (XVIII).