[OH-:1].[Na+].Cl.[NH2:4]O.[CH2:6]([O:8][C:9](=[O:22])[C:10](=[O:21])[CH:11]([CH3:20])[C:12]([CH:14]1[CH2:19][CH2:18][CH2:17][CH2:16][CH2:15]1)=O)[CH3:7].Cl>O.C(OCC)(=O)C>[CH2:6]([O:8][C:9](=[O:22])[C:10](=[O:21])[CH:11]([CH3:20])[C:12]([CH:14]1[CH2:19][CH2:18][CH2:17][CH2:16][CH2:15]1)=[N:4][OH:1])[CH3:7]
Sodium hydroxide (0.99 g, 24.7 mmol) was dissolved in 5.5 mL of water. Hydroxylamine hydrochloride (1.71 g, 24.7 mmol) was added and the reaction mixture was stirred until complete dissolution was achieved. 4-Cyclohexyl-3-methyl-2,4-dioxo-butyric acid ethyl ester (5.15 g, 21.5 mmol) was added and the resulting mixture was stirred at ambient temperature for 16 h. Ethyl acetate (20 mL) and 1M hydrochloric acid (10 mL) was added, and the aqueous layer was extracted with additional ethyl acetate (4×20 mL). The organic layers were combined, dried over MgSO4 and concentrated. The crude oil was purified by chromatography (0-30% EtOAc/hexanes) to give 3.1 g of the title compound. MS: (+) m/z 256.39 (M+1).
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