Sodium borohydride → (2S)-2-(tert-butoxycarbonylamino)-5-(5,6,7,8-tetrahydroquinolin-8-ylamino)-pentanoic acid tert-butyl ester

Participants

Reaction Steps

To a solution of (2S)-5-amino-2-(tert-butoxycarbonylamino)-pentanoic acid tert-butyl ester (free base) (0.905 g, 3.11 mmol) in CH3OH (15 mL) was added 6,7-dihydro-5H-quinolin-8-one (0.504 g, 3.43 mmol) and the resultant solution was stirred at room temperature for 5 hours. Powdered NaBH4 (0.379 g, 9.98 mmol) was added, and the mixture was stirred at room temperature for 25 minutes then concentrated under reduced pressure. The residue was dissolved in CH2Cl2 (100 mL) and brine (20 mL). The phases were separated and the aqueous phase was extracted with CH2Cl2 (3×20 mL). The combined organic extracts were dried (Na2SO4) and concentrated. Purification of the crude material by column chromatography on silica gel (20:1 CH2Cl2—CH3OH) provided 0.700 g (54%) of (2S)-2-tert-butoxycarbonylamino-5-(5,6,7,8-tetrahydroquinolin-8-ylamino)-pentanoic acid tert-butyl ester as a yellow oil.

Provenance & Evidence