Controlled syntheses of 12-oxo-PDA and its 13-epimer

Stereoselective synthesis of 12-oxo-PDA starting with (1R,3S)-cyclopenten-1,3-diol monoacetate is accomplished. Key transformations are copper-catalyzed installation of the C(1)–C(8) chain onto the cyclopentene ring and construction of the C(14)–C(18) chain. Similarly, 13-epi-12-oxo-PDA was synthesized, and its [α]D was used to confirm the purity of 12-oxo-PDA (>95%) obtained by 1H NMR spectroscopy. In addition, stability of 12-oxo-PDA was investigated to eliminate possibility of epimerization to the 13-epimer.