Methanol → 4-Hydroxy-L-proline methyl ester hydrochloride

Participants

Reaction Conditions

Reaction Steps

To a suspension of trans-4-hydroxy-L-proline (100 g, 0.76 mol, 1 equivalent) in methanol (850 mL), thionyl chloride (110 mL, 1.53 mol, 2 equivalents) was added drop-wise at 0-5° C. Then the reaction mixture was stirred for 4 hours at 20-25° C. The reaction mixture was concentrated under reduced pressure. The crude material was stirred in a mixture of ethanol-methyl tert-butyl ether (1:4, 500 mL) for 30 minutes and the solid was collected by filtration. The wet cake was dried in a vacuum tray dryer for 8 hours at about 50° C. to afford the title compound. 1H NMR (300 MHz, DMSO-d6) δ ppm 2.09-2.24 (m, 2H), 3.07 (d, 1H, J=12.3 Hz), 3.35 (dd, 2H, J=4.2 Hz, J=11.7 Hz), 3.76 (s, 3H), 4.42-4.51 (m, 2H), 5.59 (bs, 1H), 9.3 (bs, 1H), 10.3 (bs, 1H).

Provenance & Evidence