C([O:4][CH:5]([CH2:17][CH2:18][S:19]([CH3:21])=[O:20])[C:6]([NH:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH3:16])=[O:7])(=O)C.[OH-].[Na+]>CO>[OH:4][CH:5]([CH2:17][CH2:18][S:19]([CH3:21])=[O:20])[C:6]([NH:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH3:16])=[O:7]To a solution of 4-(methylsulfinyl)-1-(octylamino)-1-oxobutan-2-yl acetate (5.7 g, 17.87 mmol) in methanol (75 mL) was added 1M NaOH (26.8 mL, 26.8 mmol) and the resulting solution was stirred overnight. The reaction was evaporated to a small volume and treated with EtOAc (100 mL) and 1N HCl (100 mL). The layers were separated and the organic layer was dried over magnesium sulfate, filtered and evaporated. The crude material was purified by silica gel chromatography with 0-5% methanol/dichloromethane. The desired fractions were collected and evaporated to give a white solid (3.23 g, 65%). 1H NMR (500 MHz, DMSO-d6) δ ppm 0.85 (t, J=6.83 Hz, 3 H) 1.24 (br. s., 10 H) 1.33-1.47 (m, 2 H) 1.73-1.89 (m, 1 H) 1.95-2.10 (m, 1 H) 2.51 (d, J=0.64 Hz, 3 H) 2.58-2.87 (m, 2 H) 2.99-3.14 (m, 2 H) 3.95 (dd, J=7.15, 4.29 Hz, 1 H) 5.69 (d, J=5.09 Hz, 1 H) 7.76 (t, J=5.40 Hz, 1 H). m/z 278 (MH+).
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