[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8](=O)[CH:9](O[Si](C(C)(C)C)(C)C)[C:10]2[CH:15]=[CH:14][N:13]=[CH:12][CH:11]=2)=[CH:4][CH:3]=1.[NH2:25][C:26]1[CH:31]=[CH:30][CH:29]=[C:28]([NH2:32])[N:27]=1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>C1(C)C(C)=CC=CC=1>[NH2:32][C:28]1[N:27]=[C:26]2[C:31]([C:9]([C:10]3[CH:11]=[CH:12][N:13]=[CH:14][CH:15]=3)=[C:8]([C:5]3[CH:4]=[CH:3][C:2]([F:1])=[CH:7][CH:6]=3)[NH:25]2)=[CH:30][CH:29]=11-(4-Fluorophenyl)-2-t-butyldimethylsiloxy-2-(4-pyridyl)ethanone (16) (3.45 g, 10.0 mmol), 2,6-diaminopyridine (1.09 g, 10.0 mmol), p-toluenesulfonic acid monohydrate (13.3 g, 70.0 mmol), and xylene (140 mL) were warmed to 60° C. under argon (note: all condensation reactions of this type were conducted behind an explosion shield). After 1 h at 60° C., the reaction was warmed to 135° C. for 3 h. After allowing the reaction to cool to 23° C., the top layer of xylene and p-toluenesulfonic acid was decanted from the bottom layer of gummy product residue. The lower product layer was partitioned between saturated bicarbonate (100 mL), and ethyl acetate (250 mL). The ethyl acetate layer was washed with brine (1×100 mL), and dried (Na2SO4). After concentration in vacuo, the residue was purified by applying flash chromatography (2 liters of ethyl acetate:hexane 7:3 followed by 100% ethyl acetate) to afford the cleanly separated regioisomer (17): Mass Spectrum (CI) 305 (MH+).
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