C[Si]([N-][Si](C)(C)C)(C)C.[Na+].[C:11]([O:14][CH2:15][CH3:16])(=[O:13])[CH3:12].Cl[C:18]1[S:19][C:20]2[CH:26]=[C:25]([C:27]([O:29][C:30]([CH3:33])([CH3:32])[CH3:31])=[O:28])[CH:24]=[CH:23][C:21]=2[N:22]=1.Cl>C1COCC1.C1(C)C=CC=CC=1>[CH2:15]([O:14][C:11](=[O:13])[CH2:12][C:18]1[S:19][C:20]2[CH:26]=[C:25]([C:27]([O:29][C:30]([CH3:33])([CH3:32])[CH3:31])=[O:28])[CH:24]=[CH:23][C:21]=2[N:22]=1)[CH3:16]To a solution of sodium bis(trimethylsilyl)amide (4.9 mL of a 1M solution in THF, 4.90 mmol) in toluene (10 mL) at −78° C. was added dropwise ethyl acetate (0.26 mL, 2.7 mmol) and the mixture stirred for 1 h then a solution of Compound 188a (0.60 g, 2.2 mmol) in toluene (5 mL) was added over a 7 minute period. The resulting mixture was maintained at −78° C. for 1 h then slowly warmed to 0° C. over a period of 1.5 h. The reaction mixture was poured into a 1 N HCl solution and extracted with EtOAc. The combined extracts were washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel chromatography eluting with 0-50% EtOAc/hexanes to give Compound 188b (480 mg, 67% yield) as a white solid. LCMS=2.13 min using analytical method (B), 322.0 (M+H). 1H NMR (400 MHz, CDCl3) δ 8.57-8.52 (m, 1H), 8.11 (dd, J=8.6, 1.5 Hz, 1H), 8.04-7.98 (m, 1H), 4.32-4.25 (m, 2H), 4.20 (s, 2H), 1.63 (s, 9H), 1.32 (t, J=7.2 Hz, 3H).
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