In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), a solution of 2-methyl-5-(m-tolyl)oxazole-4-carboxylic acid (WO 2009/077990) (1.38 g, 6.33 mmol) in dry toluene (63 mL) was treated with DMF (0.02 mL, 0.3 mmol) followed by oxalyl chloride (0.84 mL, 9.50 mmol) and the reaction mixture was stirred at rt for 50 min. The solvent was then removed under reduced pressure. The resulting acid chloride was dissolved in CH2Cl2 (23 mL) and added dropwise to a solution of 1-(2-((4-amino-2H-1,2,3-triazol-2-yl)methyl)oxazol-4-yl)ethanone (WO 2009/077990) (1.31 g, 6.33 mmol) and DIPEA (3.3 mL, 18.99 mmol) in CH2Cl2 (40 mL) and the resulting mixture was stirred at rt overnight. Water was added, the layers were separated, and the aq. layer was extracted three times with CH2Cl2. The combined org. layers were washed with brine, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. Purification of the residue by FC (4:6 hept-EA) gave the title compound which was re-crystallized from hot EtOH to give a white solid: TLC: rf (4:6 hept-EA)=0.35. LC-MS-conditions 02: tR=0.99 min, [M+H]+=407.22.
