1,4-Dioxane hydrochloride → 3-methoxy-2,2-dimethyl-3-oxopropyl (3S,4S)-3-({[(1R)-1-(1-naphthyl)ethyl]amino}methyl)-4-phenylpyrrolidine-1-carboxylate

A 2.5 ml toluene solution of 227 mg of 3-methoxy-2,2-dimethyl-3-oxopropyl (3R,4S)-3-({(tert-butoxycarbonyl)[(1R)-1-(1-naphthyl)ethyl]amino}methyl)-4-phenylpyrrolidine-1-carboxylate was mixed with 1.5 ml of 4 M hydrogen chloride/1,4-dioxane at room temperature and stirred overnight at room temperature. The reaction solution was concentrated under a reduced pressure, and the thus obtained residue was mixed with toluene, washed with saturated sodium bicarbonate aqueous solution and saturated brine in that order and dried with anhydrous sodium sulfate. This was concentrated under a reduced pressure, and the thus obtained residue was purified by a silica gel column chromatography (toluene-methanol) to obtain 3-methoxy-2,2-dimethyl-3-oxopropyl (3S,4S)-3-({[(1R)-1-(1-naphthyl)ethyl]amino}methyl)-4-phenylpyrrolidine-1-carboxylate as a crude product.