Into a dry flask was placed a solution of [(4RS, 1E)-4-hydroxy-4-methyl-1-octenyl]tri-n-butyltin (973 mg, 2.26 mmol) in dry tetrahydrofuran (5 ml) under nitrogen atmosphere and the mixture was cooled to 0° C. The solution was dropped with 5.1 ml (4.48 mmol) of a diethyl ether solution of methyllithium (0.88 mol/liter), warmed to room temperature and stirred for 2 h. After cooling to −40° C., copper (I) cyanide (200 mg, 2.26 mmol) was added and dissolved by letting the temperature rise gradually to 0° C. The reaction liquid was cooled to −78° C., dropped with boron trifluoride ether complex (283 μl, 2.26 mmol), stirred for 10 min and added with a solution of (±) methyl 7-(3-tert-butyldimethylsilyloxy-5-oxo-1-cyclopentenyl)heptanoate (500 mg, 1.4 mmol) in dry tetrahydrofuran (2 ml) was rapidly added. After stirring for 30 min , 20 ml of a saturated aqueous ammonium chloride/aqueous ammonia (9:1) was added, and stirring was continued for 20 min, letting the temperature rise gradually to room temperature. This mixture was extracted with ethyl acetate (70 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 522 mg (75% 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.
