[C:1]([O:5][C:6]([NH:8][C@@H:9]([C:11]([OH:13])=O)[CH3:10])=[O:7])([CH3:4])([CH3:3])[CH3:2].[C:14](=[N:17]O)([NH2:16])[CH3:15].C(Cl)CCl.C(OCC)(=O)C>O1CCOCC1.CN(C)C=O>[C:1]([O:5][C:6](=[O:7])[NH:8][C@@H:9]([C:11]1[O:13][N:17]=[C:14]([CH3:15])[N:16]=1)[CH3:10])([CH3:2])([CH3:3])[CH3:4]To a solution of N-(tert-butoxycarbonyl)-D-alanine (20 g, 106 mmol), acetamide oxime (17.3 g, 234 mmol) in 120 mL of 1,4-dioxane and 30 mL of N,N-dimethylformamide were added EDC (44.8 g, 234 mmol). The mixture was heated at 60° C. for 4 h then at 100° C. for 16 h. After cooling to ambient temperature, 300 mL of ethyl acetate was added. The mixture was washed with aqueous saturated sodium bicarbonate (2×). The combined organic extracts were dried over magnesium sulfate, filtered and concentrated. The residue was purified by silica gel chromatography (100% dichloromethane→90% dichloromethane/methanol) to give pure tert-butyl[(1R)-1-(3-methyl-1,2,4-oxadiazol-5-yl)ethyl]carbamate (6.0 g). MS 172.1 ((M-t-butyl+H)+1).
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