(2S,4R)-1-allyloxycarbonyl-4-hydroxy-2-hydroxymethylpyrrolidine → 1-(Phenylmethyl) (2S,4R)-4-hydroxy-1,2-pyrrolidinedicarboxylate

Participants

Reaction Steps

A solution of benzyl chloroformate (12.5 mL, 87.7 mL) in toluene (40 mL) was added to a solution of trans-4-hydroxy-L-proline 1 (10 g, 76.3 mmol) and NaHCO3 (16 g, 190 mmol) in H2O (165 mL) over a period of 15 minutes. After stirring at room temperature for 12 hours the two phases were allowed to separate. The aqueous phase was washed with diethyl ether (4×50 mL), cooled in an ice bath, and then acidified to pH 2 with conc. HCl. The resultant product was extracted with ethyl acetate (5×50 mL) and the combined organic extracts were dried (MgSO4) and the excess solvent evaporated in vacuo to afford a colourless viscous oil (20.30 g, 100%). [α]27D=−565° (c=0.1, MeOH). 1H NMR (CDCl3): δ 2.07-2.31 (m, 3H, H1), 3.52-3.59 (m, 2H, H3), 4.43-4.53 (m, 2H, H2,H11a), 5.8 and 5.11 (s, 2H, minor and major rotamers of H6, 1:2), 6.0 (bs, 2H, OH), 7.26-7.29 and 7.32-7.34 (m, 5H, minor and major rotamers of H arom, 1:2). IR (thin film): v=3414 (OH), 2940 (OH), 1682 (C═O), 1495, 1429, 1359 (CO2-), 1314, 1269, 1205, 1180, 1174, 1127, 1082, 1051, 993, 914, 866, 826, 769, 741, 697 cm−1. MS (EI): m/e (relative intensity): 266 (M+, 1), 265 (6), 220 (5), 176 (15), 130 (34), 108 (2), 91 (100), 86 (4), 68 (11). HRMS calcd. for C13H15NO5=265.0950 found 265.0976.

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