[C:1]([CH2:4][N:5]1[C:9](=[O:10])[CH2:8][N:7]([CH2:11][CH:12]([OH:21])[CH2:13][C:14](OCC(C)C)=[O:15])C1C(C)C)(=[O:3])[NH2:2]>CN(C)C=O.O>[OH:21][CH:12]1[CH2:11][N:7]([CH2:8][C:9]([NH:5][CH2:4][C:1]([NH2:2])=[O:3])=[O:10])[C:14](=[O:15])[CH2:13]1A solution of 11.8 g (34.3 mol) of 2-methylpropyl 3-carbamoylmethyl-Beta-hydroxy-2-(1-methylethyl)-4-oxo-1-imidazolidinebutanoate in 90 ml of dimethylformamide and 10 ml of water was gently refluxed (external temp. 130° C.) for 24 hours. The solvent was evaporated under reduced pressure. The oily residue was taken up with 40 ml of ethanol and stirred at 0° C. for 30 minutes. The precipitate was collected and crystallized from ethanol/isopropanol 1:1 to give 2.5 g of the title compound as a white powder, m.p. 158°-160° C. Mass spectrum (E.I., 70 eV, 1.5 mA), m/z=197 (M+ --H2O), 180. IR spectrum (oil mull): 3420, 3320, 3220, 1680, 1655 and 1630 cm-1.
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