Hydrochloric Acid → (2R)-2-amino-N-(8-amino-2-oxo-1,2,3,4-tetrahydroquinolin-3-yl)-4-methylpentanamide

Participants

Reaction Conditions

Reaction Steps

3,8-Diamino-3,4-dihydroquinolin-2(1H)-one dihydrochloride (9.0 g) was suspended in N,N-dimethylformaldehyde (90 mL), and triethylamine (15 mL) was added to the suspension under cooling on ice. Subsequently, N-tert-butoxycarbonyl-D-leucine monohydrate (9.87 g), 1-hydroxybenzotriazole (4.86 g), and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (7.67 g) were sequentially added to the mixture, followed by stirring at room temperature for one hour. To the resultant mixture were added saturated aqueous sodium bicarbonate solution, ethyl acetate, and water, and the mixture was subjected to extraction. The organic layer was sequentially washed with water and saturated aqueous sodium chloride solution, and was dried over sodium sulfate. The solvent was evaporated under reduced pressure, and the precipitates were filtered by use of ethyl acetate, whereby tert-butyl (2R)-1-(8-amino-2-oxo-1,2,3,4-tetrahydroquinolin-3-ylamino)-4-methyl-1-oxopentan-2-ylcarbamate (12.4 g) was yielded as a diastereomeric mixture. Subsequently, the thus-obtained tert-butyl (2R)-1-(8-amino-2-oxo-1,2,3,4-tetrahydroquinolin-3-ylamino)-4-methyl-1-oxopentan-2-ylcarbamate (7.68 g) was dissolved in ethanol (77 mL), and concentrated hydrochloric acid (34 mL) was added thereto, followed by heating to 60° C. while being stirred for 30 minutes. The resultant mixture was neutralized with saturated aqueous sodium bicarbonate solution under cooling on ice and was then subjected to extraction with chloroform. The organic layer was washed with saturated aqueous sodium chloride solution and dried over sodium sulfate. The solvent was evaporated under reduced pressure, and the thus-recovered residue was purified through silica gel column chromatography (chloroform:methanol=15:1), whereby the title compound (diastereomer of lower polarity: 2.85 g, diastereomer of higher polarity: 2.73 g) was yielded.

Provenance & Evidence