1-(1,1-Dimethylethyl) 2-ethyl (2S)-5-oxo-1,2-pyrrolidinedicarboxylate → (S)-2-tert-Butoxycarbonylamino-5-oxo-hexanoic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of (S)-5-oxo-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-ethyl ester (20 g, 10 mmol) in dry THF (150 mL) was cooled to −50° C., and then methylmagnesium bromide (31 mL, 93.28 mmol) was added dropwise at a temperature between −50 and −44° C. in 30 min. The reaction mixture was stirred at −43° C. for 2 h and placed in a freezer (ca. −20° C.) overnight. The mixture was quenched with sat. NH4Cl solution and extracted with EtOAc. The combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure to give the crude product, which was purified by column chromatography (8:1-3:1 petroleum ether:EtOAc) to give the title intermediate (38 g) as light yellow oil. 1H NMR (400 MHz, CDCl3): δ(ppm) 5.11-5.09 (m, 1H), 4.25-4.24 (m, 1H), 4.19 (q, J=7.2 Hz, 2H), 2.63-2.52 (m, 2H), 2.15 (s, 3H), 2.12-2.08 (m, 1H), 1.92-1.82 (m, 1H), 1.44 (s, 9H), 1.28 (t, J=7.2 Hz, 3H).

Provenance & Evidence