(2S,4R)-1-[(benzyloxy)carbonyl]-4-methoxypyrrolidine-2-carboxylic acid → benzyl (2S,4R)-2-(hydroxymethyl)-4-methoxypyrrolidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution of borane-tetrahydrofuran complex in THF (1M, 53.0 mL, 53.0 mmol, 3.50 equiv) was added to a solution of (2S,4R)-1-[(benzyloxy)carbonyl]-4-methoxy-2-pyrrolidinecarboxylic acid (3-2, 4.23 g, 15.1 mmol, 1 equiv) in THF (200 mL) at 0° C. The resulting mixture was warmed to 23° C. and stirred for 1 h. Excess borane was carefully quenched with water. The mixture was then partitioned between a 1:1 mixture of saturated sodium carbonate solution and brine (300 mL) and ethyl acetate (300 mL). The organic layer was dried over sodium sulfate and concentrated. The residue was purified by flash column chromatography (100% hexane initally, grading to 100% EtOAc) to provide benzyl (2S,4R)-2-(hydroxymethyl)-4-methoxy-1-pyrrolidinecarboxylate (3-3) as a colorless oil. 1H NMR (300 MHz, CDCl3) major rotamer: δ7.37-7.25 (br m, 5H), 5.18 (d, 1H, J=12.4 Hz), 5.13 (d, 1H, J=12.2 Hz), 4.51 (dd, 1H, J=8.3,2.2 Hz), 3.86 (m, 1H), 3.78 (dd, 1H, J=11.7, 2.2 Hz), 3.72 (br d, 1H, J=11.7 Hz), 3.61 (ddd, 1H, J=9.8, 7.4, 2.2 Hz), 3.44 (dd, 1H, J=12.2, 4.4 Hz), 3.30 (s, 3H), 2.18 (m, 1H), 1.64 (m, 1H).

Provenance & Evidence