930.2 mg (27.3 mMol) of NaH (as a 60% strength dispersion in mineral oil) are added, under nitrogen, to a cooled, stirred solution of 10.0 g (22.7 mMol) of 2-[1-(4-chlorobenzyl)-1H-indol-3-yl]-2-oxo-N-quinolin-6-ylacetamide in 500 ml of dry THF. The solution is stirred at 0° C. until a yellow precipitate separates out and, after that, stirred for a further 15 minutes. After that, 2.58 g (27.3 mMol) of methyl chloroformate are added dropwise at a temperature below +5° C. The reaction is monitored by thin layer chromatography (eluent: n-heptane/ethyl acetate 1/1 RF=0.11). The reaction mixture is poured into water and the resulting mixture is extracted with ethyl acetate; the organic phase is washed with a saturated solution of sodium chloride and dried over anhydrous MgSO4. Evaporating off the solvent yields a crude product, which is purified by column chromatography (n-heptane/acetone 2/1) in order to give 3. Thin layer chromatography shows that 3 still contains slight impurities, which can be removed by stirring the crude 3 with acetone for 1 h. Filtration yields 3 as pale yellow crystals.
