Nitrogen → (R)-2-(2-ethoxy-5-oxo-tetrahydrofuran-3-ylcarbamoyl)-pyrrolidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

To a solution of (R )-2-(2-ethoxy-5-oxo-2,5-dihydrofuran-3-ylcarbamoyl)-pyrrolidine-1-carboxylic acid tert-butyl ester (X, R1=Et) (0.09 g, 0.27 mmol) in toluene previously degassed with N2 (20 mL) in a high pressure reactor in a nitrogen filled glove bag, was added (−)-1,2-bis((2R,5R)-2,5-diethyl-phospholano)benzene-(cyclooctadiene)rhodium(I) trifluoromethanesulfonate (5-15 mg). The reactor was sealed and pressurized with hydrogen (950 psi, 65 atm) and was let stand at room temperature for 2 d. Solvent was evaporated and the residue was purified by flash chromatography (SiO2) eluted with 1.5:98.5 methanol:dichloromethane to provide (R)-2-(2-ethoxy-5-oxo-tetrahydrofuran-3-ylcarbamoyl)-pyrrolidine-1-carboxylic acid tert-butyl ester (0.092 g, quant yield) as a colorless oil. Chiral HPLC (chiralpak-AD column, eluted with 1:9 ethanol:hexanes): isomer Ib-35.4%, isomer Id-56.4%, (mixture of isomers Ia and Ic)-8.2%. 1H-NMR (500 MHz, CDCl3) δ 7.60 (br s, 0.25H), 7.40 (br s, 0.25H), 6.5 (br m, 0.25H), 5.38 (d, J=5 Hz, 0.5H), 5.27 (s, 0.5H), 4.65 (br, 0.5H), 4.20 (br m, 1.5H), 3.85 (m, 0.5H), 3.77 (m, 0.5H), 3.57 (m, 1H), 3.30 (m, 2H), 2.95 (m, 0.5H), 2.80 (br m, 0,5H), 2.30 (br m, 2H), 1.85 (br s, 3H), 1.37 (s, 9H), 1.20 (t, J=7 Hz, 1.5H), 1.15 (t, J=7 Hz, 1.5H) ppm.

Provenance & Evidence