Hydrochloric Acid → 1-tert-Butyl 2-methyl (2S,4R)-4-((methanesulfonyl)oxy)pyrrolidine-1,2-dicarboxylate

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Reaction Steps

To a solution of trans-1-t-butoxycarbonyl-4-hydroxy-L-proline (8.5 g) in tetrahydrofuran (110 ml) at -30° C., triethylamine (12.8 ml) and methanesulfonyl chloride (6.27 ml) are added. The mixture is stirred at the same temperature for 30 minutes. To the mixture triethylamine (5.13 ml) and methanol (30 ml) are added. The mixture is stirred for 30 minutes. The reaction mixture is acidified with 1N-hydrochloric acid (37 ml) and extracted with ethyl acetate. The extract is successively washed with water, aqueous sodium hydrogen carbonate, water and saturated brine, dried over sodium sulfate, and concentrated in vacuo. The residue is purified by silica gel column chromatography and recrystallized from toluene-petroleum ether to give (2S,4R)-1-t-butoxycarbonyl-4-methanesulfonyloxypyrrolidine-2-carboxylic acid methyl ester (9.16 g). Colorless crystals. Yield: 77%. mp. 86° to 87° C. NMR δ(CDCl3) ppm: 1.42, 1.47, 1.50(3×s, 9H), 2.19 to 2.35(m, 1H), 2.48 to 2.75(m, 1H), 3.06, 3.07, 3.26(3×s, 3H), 3.59 to 4.12(m, 5H), 4.35 to 4.60(m, 1H), 5.18 to 5.32(m, 1H). IR ν (CHCl3) cm-1 : 1748, 1698.

Provenance & Evidence