Lithium Hydroxide → (R)-1-Boc-4,4-difluoro-3,3-dimethylpyrrolidine-2-carboxylic acid

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Reaction Conditions

Reaction Steps

To a solution of methyl ester F4 (4.7 g, 16 mmol) in methanol (100 mL) was added a solution of LiOH (6.8 g, 160 mmol) in water (50 mL) and the solution was heated at 50° C. for 14 h. The methanol was removed in vacuo and the remaining solution was diluted with water (200 mL). The aqueous solution was extracted with ether (2×200 mL), acidified with 1N HCl (200 mL) and extracted again with ether (2×200 mL). The combined organics were washed with brine (1×200 mL), dried with magnesium sulfate and concentrated in vacuo. The while solid was dried overnight at 40° C. under vacuum. Isolated yield: 4.3 g (95%). 1H NMR (400 MHz, DMSO-d6): □ 12.95 (bs, 1H), 3.93 (s, 1H), 3.84–3.74 (m, 2H), 1.38 (s)+1.33 (s) (9H), 1.19 (s, 3H), 1.01 (s, 3H); 19F NMR (376 MHz, DMSO-d6): □ −111.4 (dt, J=227, 13 Hz)+−112.4 (dt, J=227, 13 Hz) (1F), −113.5 (dt, J=227, 14 Hz) +−113.9 (dt, J=227, 15 Hz) (1F); MS-APCI (m/z+): 180.1, (m/z−): 278.

Provenance & Evidence