3,4-Diaminopyridine → 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid (4-aminopyridin-3-yl)amide

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Reaction Steps

In a 500 ml round-bottomed flask, a mixture of 730 mg of 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid obtained according to stage 2 of Example 1, 373 mg of 3,4-diaminopyridine, 721 mg of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDCI) and 508 mg of 1-hydroxybenzotriazole (HOBt) in 60 ml of dimethylformamide is stirred for 19 hours at ambient temperature. The reaction medium is evaporated to dryness under vacuum and the solid residue is taken up in 50 ml of water. The precipitate is filtered off and the solid is washed successively with 3 times 80 ml of water, 3 times 80 ml of a saturated solution of sodium bicarbonate and again with 3 times 80 ml of water. The solid is dissolved in methanol and the solvent is evaporated to dryness under vacuum. The residue is chromatographed on silica gel (15-40 μm), elution being carried out with a gradient of methanol (5% to 10% v/v) in dichloromethane and then a mixture of dichloromethane and 5N ammoniacal methanol (90/10 v/v). 220 mg of 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid (4-aminopyridin-3-yl)amide are obtained in the form of a solid, the characteristics of which are the following:

Provenance & Evidence