A mixture of (6S)-8-benzyl-6-methyl-3-(morpholin-4-yl)-6,7,8,9-tetrahydropyrazino[2,3-f][1,4]oxazepine (70 mg), 20% Pd(OH)2/C (70 mg) and methanol (2 mL) was stirred under a hydrogen atmosphere at 50° C. for 2 hr. Insoluble material was filtered off, and the filtrate was concentrated under reduced pressure. The residue was purified by basic silica gel column chromatography (solvent gradient; 20→100% ethyl acetate/hexane) and recrystallized (ethyl acetate-hexane) to give the title compound (11.1 mg, 21%) as colorless crystals.
