To a round bottom flask was added pyridine-2-carboxylic acid (3-amino-adamantan-1-yl)-amide (3.10 g, 11.0 mmol, Intermediate 2), 6-methylpyrazine-2-carboxylic acid (1.83 g, 13.3 mmol; RihaChcm, Kostalov, Czech Republic) and methylene chloride (120 mL). To the solution was then added PyBOP® (6.90 g, 13.3 mmol) followed by triethylamine (3.85 mL, 27.6 mmol) and the reaction was stirred for two hours at room temperature. The reaction was transferred to a 500-mL separatory funnel with methylene chloride (50 mL) and saturated aqueous sodium bicarbonate (150 mL), and extracted with methylene chloride. The organic layer was separated and the aqueous layer was extracted again with methylene chloride (2×75 mL). The combined organic layers were washed with brine (150 mL), dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified on a RP-HPLC/MS purification system (Gradient: acetonitrile in water, 27-95%, in 3.5 min with a shallow gradient from 30-60% between 0.75-3.4 min and a cycle time of 5 min. Flow rate: 100 mL/min. Mobile phase additive: 38 mM of ammonium acetate. Column: Inertsil® C8, 30×50 mm, 5 μm particle size (GL Sciences, Tokyo, Japan). Mobile phase and column temperature: 50° C.). Fractions were then concentrated under reduced pressure to remove most of the acetonitrile, the resulting aqueous layer was made basic with solid sodium carbonate (pH>10) and the aqueous layer was extracted with ethyl acetate (3×200 mL). The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure to afford 3.21 g (74%) of the title compound, 6-methyl-pyrazine-2-carboxylic acid {3-[(pyridine-2-carbonyl)-amino]-adamantan-1-yl}-amide, as a white solid. 1H NMR (400 MHz, CDCl3) δ 9.17 (s, 1H), 8.58 (s, 1H), 8.54-8.50 (m, 1H), 8.17 (dt, J=7.8, 1.0 Hz, 1H), 8.06 (br s, 1H), 7.85 (td, J=7.7, 1.7 Hz, 1H), 7.77 (br s, 1H), 7.42 (ddd, J=7.6, 4.8, 1.3 Hz, 1H), 2.61-2.57 (m, 5H), 2.40-2.28 (m, 4H), 2.27-2.19 (m, 2H), 2.18-2.08 (m, 4H), 1.78-1.68 (m, 2H). ESI-MS m/z: 392.0 (M+H)+.
