The divergent synthesis of cis-, 4a-epi-cis-, 2-epi-cis-, and trans-decahydroquinoline-type poison-frog alkaloids was achieved from the known chiral acetate 5 using a stereoselective Michael-type conjugate addition reaction and an intramolecular aldol-type cyclization with epimerization. The conformational control was achieved on the basis of the A(1,3) strain in the starting material and the stereoelectronic effect. More specifically, the synthesis of cis-251 A, cis-209 J-1, cis-223F-1, 4a-epi-cis-251 A, 2-epi-cis-251 A, and trans-251 A bearing a seven-carbon chain at the alpha-position of the nitrogen atom on the piperidine nucleus was also realized. These compounds are expected to show selective and potent inhibitory activities toward nicotinic acetylcholine receptors.