Pyridine → (S)-2-[(azepane-1-carbonyl)-amino]-4-methyl-pentanoic acid benzyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of triphosgene (15.7 g, 52.9 mmol) in CH2Cl2 (600 mL) was cooled to −10° C. under a nitrogen atmosphere. The solution was treated dropwise with a solution of (S)-2-amino-4-methyl-pentanoic acid benzyl ester (28.1 g, 0.127 mol) and pyridine (26 mL, 0.32 mol) in 150 mL of CH2Cl2. The resulting solution was stirred at −10° C. for 90 minutes and then treated with a solution of hexamethyleneimine (22 mL, 0.38 mmol) in 75 mL of CH2Cl2. The resulting solution was stirred for 48 hours at room temperature. The reaction mixture was concentrated, and the residue was dissolved in ether and washed with 1N HCl solution, water, and saturated aqueous CuSO4 solution. The organic layer was dried (Mg2SO4), treated with activated charcoal, and filtered. The filtrate was concentrated to approximately ½ volume and treated with hexane. The resulting suspension was stored overnight at −10° C. The solid was collected by filtration, washed with hexane, and dried under vacuum to give (S)-2-[(azepane-1-carbonyl)-amino]-4-methyl-pentanoic acid benzyl ester as a white solid (38.6 g, 88%); mp 87-88° C.

Provenance & Evidence