[CH3:1][Si:2]([CH3:13])([CH3:12])[CH2:3][CH2:4][O:5][CH2:6][N:7]1[CH:11]=[CH:10][N:9]=[CH:8]1.N#C[Br:16].CCOC(C)=O>C(#N)C>[Br:16][C:8]1[N:7]([CH2:6][O:5][CH2:4][CH2:3][Si:2]([CH3:13])([CH3:12])[CH3:1])[CH:11]=[CH:10][N:9]=1To a solution of 107 (100 mg, 0.50 mmol) in acetonitrile (1 mL) at room temperature was added cyanogen bromide (107 mg, 1.0 mmol) and the mixture was allowed to stir at room temperature for 3 h, concentrated to dryness and partitioned between EtOAc and water. The organic phase was collected, dried over anhydrous sodium sulfate and concentrated to dryness. The residue was purified by column chromatography (eluents EtOAc/hexane 25:75, then EtOAc), to afford the title compound 108 (45 mg, 32% yield) as a colorless oil. MS (m/z) 277.0/279.0 (M+H).
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