Diisopropylethylamine → (2S,5S)-ethyl 1-((S)-2-(methoxycarbonylamino)-3-methylbutanoyl)-5-methylpyrrolidine-2-carboxylate

Participants

Reaction Steps

To a cold (0-4° C.) stirred solution of ethyl (2S,5S)-5-methylpyrrolidin-1-ium-2-carboxylate (7 g, 24.4 mmol) (J. Med. Chem. 2006, 49, 3520-3535), (2S)-2-(methoxycarbonylamino)-3-methyl-butanoic acid (4.5 g, 25.6 mmol), and HATU (9.7 g, 25.6 mmol) in DMF (66 ml) is added DIPEA (12.7 ml, 73.3 mmol). The resultant mixture is slowly warmed up to rt and stirred for 20 hours. The reaction mixture is diluted with water and extracted with ethyl acetate. The combined extracts are washed with sodium bicarbonate, brine, dried (Na2SO4) and concentrated. The residue is purified by flash column chromatography on silica gel using ethyl acetate-hexanes (3:7 to 4:6) as eluent to afford ethyl (2S,5S)-1-[(2S)-2-(methoxycarbonylamino)-3-methyl-butanoyl]-5-methyl-pyrrolidine-2-carboxylate (5.6 g, 73%) as a white solid.

Provenance & Evidence