[NH:1]1[C:5]2[CH:6]=[CH:7][C:8]([C:10]([OH:12])=[O:11])=[CH:9][C:4]=2[N:3]=[N:2]1.[H-].[Na+].[CH3:15][C:16]1([CH3:24])[CH2:20][O:19][CH2:18][N:17]1[C:21](Cl)=[O:22].O>O1CCCC1.CN(C)C=O>[CH3:15][C:16]1([CH3:24])[CH2:20][O:19][CH2:18][N:17]1[C:21]([N:1]1[C:5]2[CH:6]=[CH:7][C:8]([C:10]([OH:12])=[O:11])=[CH:9][C:4]=2[N:3]=[N:2]1)=[O:22]
A solution of 1H-benzo[d][1,2,3]triazole-5-carboxylic acid (3 g, 18.39 mmol) in a mixture of tetrahydrofuran (90 mL) and dimethylformamide (50 mL) was added dropwise to a stirred suspension of sodium hydride (1.839 g, 46 mmol) in tetrahydrofuran (30 mL) at 0° C. The suspension was allowed to stir at room temperature for 30 minutes before adding dropwise, at 0° C., a solution of 4,4-dimethyloxazolidine-3-carbonyl chloride (3.16 g, 19.31 mmol) in tetrahydrofuran (10 mL). The reaction mixture was allowed to stir at room temperature for 4 h. Water was added at 0° C. and the solvent was evaporated. A mixture of dichloromethane/isopropanol (7:3) was added and the organic layer was separated. The aqueous layer was re-extracted with dichloromethane and the combined organic layers were dried (MgSO4), filtered and evaporated. The orange residue was recrystallised from isopropanol to give a beige solid (840 mg) that was used in the next step without further purification.
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