1-Hydroxybenzotriazole → [(S)-2-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-3-phenyl-propionylamino]-thiazole-4-carboxylic acid methyl ester

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반응 단계

A solution of 2-((S)-2-amino-3-phenyl-propionylamino)-thiazole-4-carboxylic acid methyl ester (prepared as described in example 3, step c) (0.61 g, 2.0 mmol), (R)-tert-butoxycarbonylamino-phenylacetic acid (0.55 g, 2.2 mmol), diisopropylethylamine (1.40 mL, 7.88 mmol) and 1-hydroxybenzotriazole (0.324 g, 2.40 mmol) in N,N-dimethylformamide (5 mL) was stirred in an ice bath for 5 minutes To the cooled yellow-orange solution was added O-benzotriazol-1-yl-N,N,N′,N′-tetramethyluronium hexaflurorophosphate (0.91 g, 2.40 mmol). The reaction mixture was stirred for 5 minutes and the ice bath was removed and stirring continued for 1 hour. The reaction mixture was then diluted with ethyl acetate, washed brine and the aqueous layer extracted with ethyl acetate. The combined organic extracts were passed through a pad of sodium sulfate layered on the top of a pad of silica gel contained in a 60 mL vacuum filtration funnel. Residual material was eluted from the pad of sodium sulfate and silica gel with ethyl acetate and the filtrate was concentrated in vacuo to give —[(S)-2-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-3-phenyl-propionylamino]-thiazole-4-carboxylic acid methyl ester which was taken into dry dichloromethane (10 mL) under argon and cooled in an ice bath. To this was added trifluoroacetic acid (5 mL, 64.9 mmol) and the mixture stirred at 0° C. for 2 hours. The reaction mixture was then concentrated to dryness. The residue was taken into dichloromethane and precipited with ether and the suspension was stirred for 15 minutes. The solid was isolated by filtration and washed with ether and dried to give a tan solid. The solid was taken into dichloromethane and washed with saturated aqueous sodium bicarbonate solution. The organic layer was separated, dried over sodium sulfate, filtered, concentrated and dried to give 2-[(S)-2-((R)-2-amino-2-phenyl-acetylamino)-3-phenyl-propionylamino]-thiazole-4-carboxylic acid methyl ester as an off white foam (0.80 g, 91%).

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