Into a dry flask was placed a solution of [(4RS, 1E)-4-hydroxy-4-methyl-1-octenyl]tri-n-butyltin (1.36 g, 3.15 mmol) in dry tetrahydrofuran (5 ml) under nitrogen atmosphere, and the mixture was cooled to 0° C. To this solution was dropped 5.7 ml (5.99 mmol) of a diethyl ether solution of methyllithium (1.05 mol/liter), and stirring was continued for 1 h, letting the temperature rise gradually to room temperature. After cooling to −40° C., copper (I) cyanide (141 mg, 1.58 mmol) was added and dissolved by letting the temperature rise gradually to 0° C. This reaction liquid was cooled to −78° C. and added with a solution of (±) methyl 7-(3-tert-butyldimethylsilyloxy-5-oxo-1-cyclopentenyl)heptanoate (318 mg, 0.9 mmol) in dry tetrahydrofuran (1.5 ml) was rapidly added. After stirring for 5 min, 20 ml of a saturated aqueous ammonium chloride/aqueous ammonia (9:1) was added, and stirring was continued for 30 min , letting the temperature rise gradually to room temperature. This mixture was extracted with ethyl acetate (80 ml) two times, and the combined organic layer was washed with a saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate, and concentrated in vacuo to remove solvent. The residue was purified by silica gel column chromatography [ethyl acetate/hexane (1/5)] to give 413 mg (96% yield) of (±)-methyl(16RS, 13E)-11-tert-butyldimethylsilyloxy-16-hydroxy-16-methyl-9-oxoprost-13-en-1-oate as a colorless oil. The spectral data of IR and 1H NMR were identical with those of the example 2.
