Palladium-catalyzed reaction of TBS ether of 4-cyclopentene-1, 3-diol monoacetate (> 95% ee) with an anion derived from methyl malonate and a base such as t-BuOK and LDA proceeded highly efficiently and reproducibly. The product obtained in> 90% isolated yield was transformed in five steps into the key cyclopentenone possessing the α-chain at the γ position. Aldol reaction of this enone with the ω-chain aldehyde afforded the aldol adduct, ...