合成路线1

Treatment of the optically pure lactone (I) with lithium dimethyl methylphosphonate in tetrahydrofuran gives hemiacetal (II), which is oxidized to the diketone (III) using Jones' reagent in acetone. Then in the key step, compound (III) cyclizes to enone (IV) using potassium carbonate and 18-crown-6 in warm toluene. Lithium dimethyl cuprate addition to enone (IV) in ether gives ketone (V), which is converted to acid (VI) (a 1:1 mixture of E and Z olefins at C-5) using (4-carboxybutyl)triphenylphosphorane in dimethyl sulfoxide. Cleavage of the alcohol-protecting groups in (VI) with an acetic acid-water-tetrahydrofuran mixture followed by chromatography to remove the 5-E isomer affords 9-methylcarbacyclin (VII). Finally, treatment of (VII) with calcium oxide in tetrahydrofuran gives U-61431F (ciprostene calcium).