| 摘要 |
The invention relates to compounds of the formula I <IMAGE> (I) in which R1, R2 and R4 represent optionally substituted aliphatic, alicyclic, alicyclic-aliphatic, aromatic, araliphatic, heteroaromatic or heteroaromatic-aliphatic radicals, with R2, if not already covered by the above-mentioned definitions, denoting the side-chain, which is protected if necessary, of a naturally occurring alpha -amino acid, R4 can additionally represent <IMAGE> R3 denotes an optionally substituted aliphatic, alicyclic, aromatic or araliphatic radical, or R3 and R4 form, together with the atoms carrying them, a mono-, bi- or tricyclic heterocyclic ring system, agents containing these, and the use thereof as pharmaceuticals having a psychotropic action for the prophylaxis of disorders of the central nervous system, especially having a nootropic action for the treatment of cognitive dysfunctions. |
