[C:1]([OH:5])([CH3:4])([CH3:3])[CH3:2].[C:6](Cl)(=[O:10])[C:7](Cl)=[O:8].[NH:12]1[CH:16]=[CH:15][N:14]=[CH:13]1>C1COCC1>[N:12]1([C:6](=[O:10])[C:7]([O:5][C:1]([CH3:4])([CH3:3])[CH3:2])=[O:8])[CH:16]=[CH:15][N:14]=[CH:13]158.5 g (0.79 mol) of tert-butanol are added with stirring at 0° C. under argon to 100 g (0.79 mol) of oxalyl chloride in 1.3 l of THF. After stirring at 0° C for 1 hour, 161 g (2.37 mol) of imidazole in 0.7 l of THF are added dropwise in the course of 60 min. After a further 15 min, the mixture is filtered, the solid is washed with 0.5 l of THF, and the filtrate is concentrated to a volume of 1 l, filtered again, then completely concentrated, allowed to stand overnight at 0° C. under argon and again filtered through a frit.
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