| abstract |
The invention relates to compounds of the formula I. wherein R¹, R² and R₄ represent optionally substituted aliphatic, alicyclic, alicyclic-aliphatic, aromatic, araliphatic, heteroaromatic or heteroaromatic-aliphatic radicals, where R², if not already included in the above definitions, represents the optionally protected side chain of a naturally occurring α- Amino acid means R⁴ additionally for R³ can be an optionally substituted aliphatic, alicyclic, aromatic or araliphatic radical, or R³ and R⁴ together with the atoms carrying them form a mono-, bi- or tricyclic heterocyclic ring system, compositions containing them and their use as medicaments with a psychotropic effect for the prophylaxis of disorders in the central nervous system, in particular with a nootropic effect for the treatment of cognitive dysfunctions. |