Chemical synthesis. Reagents and Conditions: a bis(pinacolato)diboron, Pd(dppf)2⋅CH2Cl2, K2CO3, 1,4-dioxane, reflux, 10 h; b Acetylchloride, Et3N, DMAP, CH2Cl2, room temperature, overnight, for 9a; Boc2O, Et3N, DMAP, CH2Cl2, room temperature, overnight, for 9b; c cyclohexanol, DMAP, THF, 0 °C, 3 h; d KN(TMS)2, toluene, 2-methyl-3-amino-5-bromopyridine in THF, 0 °C, 0.5 h; e Pd(Ph3P)4, K2CO3, 1,4-dioxane + H2O, reflux, 12 h; f 2 mol/L HCl, CH3OH, 60 °C, overnight