CS(O[CH2:6][CH2:7][CH:8]([CH2:11]O)[C:9]#[N:10])(=O)=O.[C:13](=[O:26])([O:19][NH:20][C:21]([O:23][CH2:24][CH3:25])=[O:22])[O:14][C:15]([CH3:18])([CH3:17])[CH3:16].C(=O)([O-])ON(C(C)(C)C)C(OCC)=O.C(=O)([O-])[O-].[K+].[K+]>CN(C)C=O.O>[C:13](=[O:26])([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])[O:19][N:20]([CH2:6][CH2:7][C:8]([C:9]#[N:10])=[CH2:11])[C:21]([O:23][CH2:24][CH3:25])=[O:22]A mixture of 4-methylsulfonyloxy-2-(hydroxymethyl) butanenitrile (i.e. the product of Step E) (6.87 g, 0.039 mol), 1,1-dimethylethyl (ethoxycarbonyl)azanyl carbonate (7.65 g, 0.037 mol) (i.e. the product of Step F) and potassium carbonate (10.21 g, 0.074 mol) in N,N-dimethylformamide (50 mL) was stirred at room temperature for 20 h. The reaction mixture was poured onto iced water (100 mL) and extracted with diethyl ether (3×50 mL). The combined organic layers were washed with water (50 mL) and concentrated to a pale-tan oil (10.05 g). The oil was adsorbed onto Celite® (diatomaceous filter aid), and then purified by silica gel chromatography (0-100% gradient of ethyl acetate in petroleum ether as eluant). The appropriate fractions were combined to provide the title compound as a yellow oil (3.78 g).
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