[CH2:1]([O:3][C:4]([CH2:6][N:7]1[CH2:12][CH2:11][NH:10][CH2:9][CH2:8]1)=[O:5])[CH3:2].C(N(CC)CC)C.[C:20]([O:24][C:25](ON=C(C1C=CC=CC=1)C#N)=[O:26])([CH3:23])([CH3:22])[CH3:21]>O1CCOCC1>[C:20]([O:24][C:25]([N:10]1[CH2:9][CH2:8][N:7]([CH2:6][C:4]([O:3][CH2:1][CH3:2])=[O:5])[CH2:12][CH2:11]1)=[O:26])([CH3:23])([CH3:22])[CH3:21]1-(Ethoxycarbonylmethyl)-piperazine (5.00 g, 29.0 mmol) is dissolved in 35 mL of 50% aqueous dioxane. Triethylamine (4.41 g, 43.5 mmol) is added followed by 2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile (7.86 g, 31.9 mmol). The reaction is stirred for 14.5 hours at ambient temperature, then poured onto water and extracted with ethyl acetate (2×100 mL). The combined organic extracts are washed with water (3×100 mL), brine, dried over MgSO4, filtered, and concentrated in vacuo. The residue is purified via silica gel chromatography with gradient elution (20%→50% ethyl acetate in hexanes) affording the desired product as an oil. CIMS: MH+ 273.
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