Triethylamine → tert-butyl (S)-3-[tert-butoxycarbonyl-[(R)-1-(naphthalen-1-yl)ethyl]amino]pyrrolidine-1-carboxylate

Participants

Reaction Steps

To a solution of 25 g of tert-butyl 3-hydroxypyrrolidine-1-carboxylate and 25.9 g of diisopropylethylamine dissolved in 250 ml of methylene chloride was added dropwise a solution of 49 g of anhydrous trifluoromethanesulfonic acid in 50 ml of methylene chloride at −20° C. or lower. The reaction mixture was stirred for 15 minutes while maintaining it to −20° C., and to the mixture was added dropwise 125 ml of a solution of 27.4 g of (R)-(+)-1-(1-naphthyl)ethylamine in methylene chloride at −20° C. or lower, and the reaction mixture was stirred at room temperature for 4.5 hours. To the reaction mixture were added a saturated aqueous sodium bicarbonate solution and chloroform, the mixture was stirred and the liquids were separated. The organic layer was washed with water and a saturated brine, dried and the solvent was evaporated, and then, the residue was purified by silica gel column chromatography (hexane:ethyl acetate=4:1→1:1) to obtain 25.8 g of tert-butyl (R)-3-[1-(naphthalen-1-yl)ethylamino]pyrrolidine-1-carboxylate. MS•APCI (m/z): 341 [M+H]+ (2) To a solution of 36.3 g of triphosgene dissolved in 600 ml of methylene chloride was added dropwise a solution of 62.50 g of tert-butyl (R)-3-[1-(naphthalen-1-yl)ethylamino]pyrrolidine-1-carboxylate and 76.4 ml of triethylamine in 250 ml of methylene chloride at −20° C., and the mixture was stirred at room temperature for 1 hour. To the reaction mixture was added water, the mixture was stirred and the liquids were separated. The organic layer was dried, and the solvent was evaporated. To the residue were added 1.48 L of tert-butanol and 50 ml of diisopropylethylamine, and the mixture was stirred at 70° C. for 16 hours. The reaction mixture was evaporated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate=10:1→8:1) to obtain 24.98 g of tert-butyl (S)-3-[tert-butoxycarbonyl-[(R)-1-(naphthalen-1-yl)ethyl]amino]pyrrolidine-1-carboxylate and 26.83 g of tert-butyl (R)-3-[tert-butoxycarbonyl-[(R)-1-(naphthalen-1-yl)ethyl]amino]pyrrolidine-1-carboxylate, respectively. (3) To a solution of 28.9 g of tert-butyl (S)-3-[tert-butoxycarbonyl-[(R)-1-(naphthalen-1-yl)ethyl]amino]pyrrolidine-1-carboxylate dissolved in 60 ml of chloroform was added dropwise 116 ml of a solution of 4M hydrochloric acid in dioxane, and the mixture was stirred at room temperature for 16 hours. The resulting precipitates were collected by filtration, washed with diethyl ether, crystallized from ethanol-diethyl ether, washed with diethyl ether and dried to obtain 22.38 g of (S)-3-[(R)-1-(naphthalen-1-yl)ethylamino]pyrrolidine dihydrochloride (Reference example 1.005(a) in the following Reference example Table).

Provenance & Evidence