2.0 g of 2-methyl-6,11-dihydrodibenz[b,e]oxepin-11-acetic acid was dissolved in 40 ml of toluene, and 2.52 ml of diphenylphosphoryl azide and 3.12 ml of triethylamine were added thereto at room temperature and stirred for 3.5 hours at the same temperature and then for further one hour at 100° C. The reaction mixture was cooled to room temperature, and 1.92 g of 2,6-diisopropylaniline hydrochloride and 5.0 ml of triethylamine were added thereto and stirred for 30 minutes and then for further 4 hours at 100° C. The reaction mixture was cooled to room temperature, 150 ml of water was added thereto, and the mixture was extracted with ethyl acetate. The thus obtained organic layer was washed first with 1N hydrochloric acid and then with a saturated saline solution in order, and dried and then concentrated to dryness under reduced pressure. The resulting solid residue was purified by silica gel column chromatography (using an eluting solvent of 1/3 (v/v) ethyl acetate/hexane). The crude product was recrystallized from ethyl acetate to obtain 1.16 g of Compound 1.
