Novel c-3 substituted kynurenic acid derivatives with improved neuroprotective activity

The invention relates to C-3 substituted kynurenic acid derivatives with the general formula (I) wherein R1 is C1-7alkyl-, R6R7N-C1-7alkyl-, C6-10aryl-C1-7alkyl group; R2 is H or C1-7alkyl group; or R1 and R2 with the nitrogen atom to which they are attached form a saturated or partially saturated 5-7 membered, optionally benzofused heterocyclic ring, optionally comprising additional N, O, S heteroatoms and optionally being substituted; R3 is -OH, C1-7alkyl-O-, -NH2, C1-7alkyl-NH-, C6-10aryl-C1-7alkyl-NH- or -NH- -(CH2)n-NR8R9 group wherein n is an integer from 1 to 3; R4 is H, C1-7alkyl-, C6-10aryl group or a halogen atom; R5 is H or C6-10aryl group; R6 is C1-7alkyl group; R7 is C1-7alkyl group; or R6 and R7 with the nitrogen atom to which they are attached form a saturated or partially saturated 5-7 membered, optionally benzofused heterocyclic ring, optionally comprising additional N, O, S heteroatoms and optionally being substituted; R8 is C1-7alkyl group; R9 is C1-7alkyl group; R8 and R9 with the nitrogen atom to which they are attached form a saturated or partially saturated 5-7 membered, optionally benzofused heterocyclic ring, optionally comprising additional N, O, S heteroatoms and optionally being substituted; and stereoisomers, tautomers and salts thereof. The invention relates to the pharmaceutical preparations comprising the compounds and stereoisomers, tautomers and pharmaceutically acceptable salts. The compounds of the invention have neuroprotective activity, may be used for the prevention and treatment of neurodegeneration, and for slowing down the development of the conditions and diseases associated with a decline in cognitive abilities.