[O:1]=[C:2]([N:10]1[CH2:14][CH2:13][CH2:12][C@H:11]1[C:15]([O:17]C)=[O:16])[C:3](=[O:9])[C:4]([CH3:8])([CH3:7])[CH2:5][CH3:6].[Li+].[OH-].CO.Cl>O>[O:1]=[C:2]([N:10]1[CH2:14][CH2:13][CH2:12][C@H:11]1[C:15]([OH:17])=[O:16])[C:3](=[O:9])[C:4]([CH3:7])([CH3:8])[CH2:5][CH3:6]A mixture of methyl(2S)-1-(1,2-dioxo-3,3-dimethylpentyl)-2-pyrrolidinecarboxylate (2.10 g; 8.23 mmol), 1 N LiOH (15 ml), and methanol (50 ml) was stirred at 0° C. for 30 minutes and at room temperature overnight. The mixture was acidified to pH 1 with 1 N HCl, diluted with water, and extracted into 100 ml of methylene chloride. The organic extract was washed with brine and concentrated to deliver 1.73 g (87%) of snow-white solid which did not require further purification, 1H NMR (CDCl3): δ0.87 (t, 3H); 1.22, 1.25 (s, 3H each); 1.77 (dm, 2H); 2.02 (m, 2H); 2.17 (m, 1H); 2.25 (m, 1H); 3.53 (dd, 2H, J=10.4, 7.3); 4.55 (dd, 1H, J=8.6, 4.1).
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