C([O:3][C:4]([C@@:6]1([NH:11][C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:8][C@H:7]1[CH:9]=[CH2:10])=[O:5])C.[Li+].[OH-]>C1COCC1.CO.O>[C:15]([O:14][C:12]([NH:11][C@:6]1([C:4]([OH:5])=[O:3])[CH2:8][C@H:7]1[CH:9]=[CH2:10])=[O:13])([CH3:18])([CH3:16])[CH3:17]
To a solution of 1(R)-tert-butoxycarbonylamino-2(S)-vinyl-cyclopropanecarboxylic acid ethyl ester (3.28 g, 13.2 mmol) in THF (7 mL) and methanol (7 mL) was added a suspension of LiOH (1.27 g, 53.0 mmol) in water (14 mL). The mixture was stirred overnight at room temperature and quenched with 1N NaOH (15 mL) and water (20 mL). The resulting mixture was washed with ethyl acetate (20 mL), and the organic phase was extracted with 20 mL 0.5N NaOH. The combined aqueous phases were acidified with 1N HCl until pH 4 and extracted with ethyl acetate (3×40 mL). The combined organic extracts were washed with brine, dried (MgSO4), filtered and concentrated to yield the title compound as a white solid (2.62 g, 87%). 1H NMR: (DMSO-d6) 1.22-1.26 (m, 1H), 1.37 (s, 9H), 1.50-1.52 (m, 1H), 2.05 (q, J=9Hz, 1H), 5.04 (d, J=10Hz, 1H), 5.22 (d, J=17Hz, 1H), 5.64-5.71 (m, 1H), 7.18, 7.53 (s, NH (rotamers), 12.4 (br s, 1H)); MS m/z 228 (M++H).
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