[CH3:1][O:2][C:3](=[O:18])[C:4]1[CH:9]=[CH:8][CH:7]=[C:6]([C:10]2[S:11][C:12]([CH2:15][CH2:16][OH:17])=[N:13][N:14]=2)[CH:5]=1.[O:19]1[CH:24]=[CH:23][CH2:22][CH2:21][CH2:20]1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>CCOC(C)=O>[CH3:1][O:2][C:3](=[O:18])[C:4]1[CH:9]=[CH:8][CH:7]=[C:6]([C:10]2[S:11][C:12]([CH2:15][CH2:16][O:17][CH:20]3[CH2:21][CH2:22][CH2:23][CH2:24][O:19]3)=[N:13][N:14]=2)[CH:5]=1A mixture of 3-[5-(2-hydroxy-ethyl)-[1,3,4]thiadiazol-2-yl]-benzoic acid methyl ester (1.86 g), dihydropyrane (0.95 mL) and p-toluenesulfonic acid hydrate (0.13 g) in AcOEt (25 mL) was stirred at 20° C. for 1 h. The solution was diluted with AcOEt, washed with 5% NaHCO3 solution and with brine, dried and evaporated in vacuum. The residual oil was purified by chromatography on silica gel using AcOEt/hexane (1:2) as eluent to give 3-{5-[2-(tetrahydro-pyran-2-yloxy)-ethyl]-[1,3,4]thiadiazol-2-yl]-benzoic acid methyl ester (1.60 g) as a pale-yellow oil.
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