Cl.[C:2]([Si:6]([CH3:17])([CH3:16])[O:7][CH2:8][CH2:9][CH:10]1[CH2:15][CH2:14][NH:13][CH2:12][CH2:11]1)([CH3:5])([CH3:4])[CH3:3].C(N(CC)C(C)C)(C)C.[CH3:27][C:28]([O:31][C:32]([N:34]1C(C2C=CC(C#N)=CC=2)O1)=[O:33])([CH3:30])[CH3:29]>ClCCl>[C:28]([O:31][C:32](=[O:33])[NH:34][N:13]1[CH2:14][CH2:15][CH:10]([CH2:9][CH2:8][O:7][Si:6]([C:2]([CH3:3])([CH3:5])[CH3:4])([CH3:17])[CH3:16])[CH2:11][CH2:12]1)([CH3:30])([CH3:29])[CH3:27]4-[2-(t-Butyl-dimethyl-silanyloxy)-ethyl]-piperidine hydrochloride (1:1) (300 mg, 1.07 mmol) was combined with dichloromethane (15 mL) to give a light yellow suspension. N,N-Diisopropylethylamine (166 mg, 225 μl, 1.29 mmol) was added at 0° C. Subsequently 3-(4-cyanophenyl)-2-oxaziridinecarboxylic acid 1,1-dimethylethyl ester (238 mg, 965 μmol) in dichloromethane (10 mL) was added during 20 min at 0° C. and the reaction mixture was stirred for 1 h at 0° C. Afterwards the reaction mixture was concentrated in vacuo and the residue was purified by flash chromatography (silica gel, 20 g, 0% to 40% ethyl acetate in n-heptane) to deliver an oil contaminated with 4-cyano-benzaldehyde. This material was purified by a second chromatography (aminophase 10 g, ethyl acetetate/n-heptane 1/1) to give the title compound (0.23 g, 60%) as a white solid; LC-MS (ESI) 94.9%, 359.2710 (M+H)+.
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