benzyl 3-[(R)-1-(naphthalen-1-yl)ethylamino]azetidine-1-carboxylate → 3-[(R)-1-(naphthalen-1-yl)ethylamino]azetidine

Beteiligte Stoffe

Reaktionsschritte

To a solution of 5.0 g of 1-benzohydrylazetidin-3-one dissolved in 75 ml of toluene was added 2.98 ml of benzyloxycarbonyl chloride, and the mixture was stirred at 80° C. for 4 hours. The reaction mixture was evaporated, and then, to the residue were added water and ethyl acetate, the mixture was stirred and the liquids were separated. The organic layer washed with water and a saturated brine, dried and concentrated. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=19:1→4:1), and then, hexane was added thereto, and after collecting the precipitate by filtration, it washed with hexane to obtain 2.73 g of benzyl 3-oxoazetidine-1-carboxylate. (3) To a solution of 8.51 g of benzyl 3-oxoazetidine-1-carboxylate and 7.10 g (R)-(+)-1-(1-naphthyl)ethylamine dissolved in 170 ml of methylene chloride, 7.49 g of magnesium sulfate was added to the solution. The mixture was stirred at room temperature for 3 hours, and then, 9.5 ml of acetic acid and 13.18 g of sodium triacetoxy borohydride were added thereto, and the mixture was stirred at room temperature for 1 hour. To the reaction mixture was added a saturated aqueous sodium bicarbonate solution to make the mixture basic, chloroform was added to the same and the mixture was stirred, and the liquids were separated. The organic layer was dried and concentrated, and the residue was purified by NH silica gel column chromatography (hexane:ethyl acetate=4:1→1:1) to obtain 7.90 g of benzyl 3-[(R)-1-(naphthalen-1-yl)ethylamino]-azetidine-1-carboxylate. (4) To a solution of 9.45 g of benzyl 3-[(R)-1-(naphthalen-1-yl)ethylamino]azetidine-1-carboxylate dissolved in 190 ml of methanol, 1 g of palladium carbon (10% wet) was added thereto, and the reaction was carried out under hydrogen atmosphere at room temperature for 4 hours. Palladium carbon was removed, the solvent was evaporated, and the residue was purified by NH silica gel column chromatography (chloroform:methanol=1:0→19:1) to obtain 4.60 g of 3-[(R)-1-(naphthalen-1-yl)ethylamino]azetidine. To a solution of 4.60 g of 3-[(R)-1-(naphthalen-1-yl)ethylamino]azetidine dissolved in 30 ml of ethyl acetate, under ice-cooling, 13 ml of a solution of 4M hydrochloric acid in ethyl acetate was added dropwise, and the mixture was stirred for a while.

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