To a solution of (7S,8aS)-2-(tert-butoxycarbonyl)octahydropyrrolo[1,2-a]pyrazine-7-carboxylic acid (80 mg, 0.296 mmol) in dichloromethane (2 mL) was added a solution of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (68.9 mg, 0.444 mmol) and hydroxybenzotriazole hydrate (40.0 mg, 0.296 mmol) in dichloromethane (1 mL). The mixture was stirred at room temperature for 1 hour, and then diphenylmethanamine (54.2 mg, 0.296 mmol) was added. After stirring for three days the mixture was poured into water (10 mL). The mixture was extracted with dichloromethane (3×5 mL). The organic fractions were concentrated, and the residue was purified by flash chromatography (dichloromethane/methanol=25:1) to give the title compound. MS (ESI) m/z 436 (M+H)+.
