N#N.[CH3:3][O:4][C:5]([C:8]1[O:9][CH:10]=[C:11]([CH2:13][OH:14])[N:12]=1)([CH3:7])[CH3:6].CCN(CC)CC.[S:22](Cl)([CH3:25])(=[O:24])=[O:23]>C(Cl)Cl.CN(C1C=CN=CC=1)C>[CH3:25][S:22]([O:14][CH2:13][C:11]1[N:12]=[C:8]([C:5]([O:4][CH3:3])([CH3:7])[CH3:6])[O:9][CH:10]=1)(=[O:24])=[O:23]In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), a solution of (2-(2-methoxypropan-2-yl)oxazol-4-yl)methanol (31 mg, 0.18 mmol) in dry CH2Cl2 (1.4 mL) was treated at 0° C. with Et3N (0.03 mL, 0.23 mmol) followed by DMAP (2.2 mg, 0.02 mmol) and Ms-Cl (0.02 mL, 0.23 mmol). After stirring at 0° C. for 30 min, the reaction was quenched with water (10 mL). The org. layer was dried over Na2SO4, filtered, and the solvents were removed under reduced pressure to give 44 mg of crude (2-(2-methoxypropan-2-yl)oxazol-4-yl)methyl methanesulfonate as a yellow oil. LC-MS-conditions 07: tR=0.62 min, [M+H]+=250.00. A solution of this crude material (44 mg) in DMF (0.4 mL) was added to a solution of 4-nitro-2H-[1,2,3]triazole (T. E. Eagles et al. Organic preparations and procedures 2 (2), 117-119, 1970; P. N. Neuman J. Heterocycl. Chem. 8, 51-56, 1971) (203 mg of a 9.6% solution in DMF, 0.17 mmol) in DMF (0.4 mL) pre-treated for 30 min with DIPEA (0.06 mL, 0.34 mmol) and the reaction mixture was stirred for 24 h at 50° C. Water (5 mL), followed by EA (5 mL) was added. The aq. layer was extracted with EA (10 mL) and the combined org. extracts were dried over MgSO4, filtered, and the solvents were removed under reduced pressure. Purification of the residue by FC (1:1 hept-EA) gave the title compound as a yellow oil: TLC: rf (1:1 hept-EA)=0.43. LC-MS-conditions 07: tR=0.72 min, [M]+=267.96.
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