epi-Jasmonic acid (epi-JA) and tuberonic acid (TA) were synthesized from the key aldehyde, all cis-2-(2-hydroxy-5-vinylcyclopentyl)acetaldehyde (14), which was in turn prepared stereoselectively from the (1R)-acetate of 4-cyclopentene-1,3-diol (10) through S_N2-type allylic substitution with CH₂ CHMgBr followed by Mitsunobu inversion, Eschenmoser–Claisen rearrangement, and regioselective Swern oxidation of the corresponding bis-TES ether (13). Wittig reaction of the aldehyde 14 with [Ph₃P(CH₂)Me]⁺ Br ⁻ followed by oxidation afforded epi-JA (3) stereoselectivity over the trans isomer. Similarly, TA (5) was synthesized. Furthermore, the above findings were applied successfully to improve the total efficiency of the previous synthesis of 12-oxo-PDA (1).