[C:1]([C:4]1[C:9]([NH:10][C:11]([C:13]2[S:14][CH:15]=[C:16]([C:18]#[C:19][Si](C)(C)C)[N:17]=2)=O)=[C:8]([CH3:24])[C:7]([O:25][CH3:26])=[CH:6][CH:5]=1)(=[O:3])[CH3:2].CC(C)([O-])C.[K+]>C(O)(C)(C)C>[CH3:26][O:25][C:7]1[C:8]([CH3:24])=[C:9]2[C:4]([C:1]([OH:3])=[CH:2][C:11]([C:13]3[S:14][CH:15]=[C:16]([C:18]#[CH:19])[N:17]=3)=[N:10]2)=[CH:5][CH:6]=1To a suspension of compound 208b (8.71 g, 1 eq.) in tert-butanol (240 mL) was added potassium tert-butoxide (5.32 g, 2.1 eq.). The heterogeneous mixture was stirred and heated to 80° C. The solvent was then evaporated and water was added to the resulting black residue. The pH of the mixture was brought to 6 with 1N HCl. The mixture was extracted with dichloromethane. The organic layer was dried over Na2SO4, filtered, and concentrated under vacuo. The solid was purified by chromatography on silica gel to give compound 209b as an orange solid in 52% yield. 1H NMR (CDCl3, 400 MHz) δ (ppm) 2.45 (s, 3H), 3.25 (s, 1H), 3.99 (s, 3H), 6.89 (br s, 1H), 7.06 (d, J=9.09 Hz, 1H), 7.72 (s, 1H), 8.26 (d, J=9.09 Hz, 1H), 9.50 (br s, 1H); MS (ESI, EI+): m/z=297 (MH+).
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