2-(2-Benzyloxycarbonylamino-ethyl)-4-hydroxy-pyrrolidine-1-carboxylic acid tert-butyl ester → 2-(2-Benzyloxycarbonylamino-ethyl)-4-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

A solution containing 5 (10.2 g, 28.0 mmol) in DCM (100 mL) and DMSO (20 mL) was cooled to 0° C. TEA (14.1 g, 140 mmol) and SO3.pyridine complex (17.9 g, 112 mmol) were then added and the mixture stirred until homogeneous (approx. 45 min) then warmed to ambient temperature. After 3 h, the reaction mixture was diluted with water (200 mL) and diethyl ether (500 mL). The layers were separated and the organic phase was washed successively with 1N HCl, water, aqueous NaHCO3, water, and brine then dried over anhydrous Na2SO4, filtered, and concentrated. The crude product was purified by flash silica gel chromatography (2:1 to 1:1 hexanes/EtOAc) to afford 9.34 g (92%) of 6 as a pale yellow-colored oil. 1H NMR (CDCl3, 300 MHz): δ7.32 (m, 5H), 5.90 (br s, 1H), 5.09 (app dd, J=19.4, 12.2 Hz, 2H), 4.52 (m, 1H), 3.95 (br d, 1H), 3.52 (m, 2H), 2.93 (m, 1H), 2.80 (dd, J=18.3, 9.3 Hz, 1H), 2.22 (br d, 1H), 1.69 (m, 1H), 1.55 (m, 1H), 1.57 (s, 9H) ppm. Mass spectrum, m/z [363.2] (M+H)+.

Provenance & Evidence