[Cl:1][C:2]1[CH:12]=[CH:11][CH:10]=[C:9]([Si:13]([CH3:16])([CH3:15])[CH3:14])[C:3]=1[C:4]([NH:6][CH2:7][CH3:8])=[O:5].[Li]C(C)(C)C.CCCCC.C(Br)C[Br:29]>C1COCC1>[Br:29][CH2:16][Si:13]([CH3:15])([CH3:14])[C:9]1[CH:10]=[CH:11][CH:12]=[C:2]([Cl:1])[C:3]=1[C:4]([NH:6][CH2:7][CH3:8])=[O:5]To a solution of the compound of example 45 (1.28 g, 5 mmol) in THF (30 mL) at -78° C. was added a 1.7M solution of t-BuLi in pentane (6.5 mL, 11 mmol, 2.2 eq) such that the temperature was less than -70° C. The reaction was stirred at -78° C. for 1.5 h and ethylene dibromide (0.52 mL, 6.0 mmol, 1.2 eq) was added. The reaction was stirred for 15 min at -78° C. and worked up in the usual manner. The crude product was purified by RC and recrystallized from aq methanol to afford the title compound as white needles (0.30 g, 18%). m.p. 98°-99° C.
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