Three-hundred milligrams (7.5 mmols) of 60% sodium hydride were washed with petroleum ether, and then suspended in 30 ml of dimethyl sulfoxide. To the suspension were added 1.4 g (7.1 mmols) of 5,11-dihydrodibenzo[b,e][1,4]oxazepine. The mixture was stirred in a nitrogen atmosphere at room temperature for 40 minutes. To this reaction solution was added dropwise a solution of 1.7 g (6.8 mmols) of (S)-(+)-3-chloro-1-(4-cyanophenethyl)piperidine [[α]D25 =+16.7° (c=0.5, ethanol)] in 10 ml of dimethyl sulfoxide, and the mixed solution was stirred at room temperature for 17 hours and at 40° C. for 6 hours. The reaction solution was poured into ice water, and extracted with ethyl acetate. The organic layer was washed with water and with a saturated aqueous solution of sodium chloride in this order, and dried. Subsequently, the solvent was distilled off under reduced pressure. The resulting residue was subjected to column chromatography, and eluted with a mixed solvent of ethyl acetate and hexane at a ratio of 1:2. This mixed solvent was distilled off under reduced pressure to give 0.4 g of (R)-(+)-5,11-dihydro-5-[1-(4-cyanophenethyl)-2-pyrrolidinylmethyl]dibenzo[b,e][1,4]oxazepine as a pale yellow oil in a yield of 14%.
