Abstract: Compounds of formula I ##STR1## wherein R.sub.1 is a cyano, nitro, benzoyl, acetyl, amido or alkoxycarbonyl group;R.sub.2 is substituted aryl- or heterocyclic residue;R.sub.3 is alkoxycarbonyl group;R.sub.4 and R.sub.5, being the same or different, are hydrogen, alkyl, aryl or heterocyclic groups;Y is oxygen, sulphur or substituted or unsubstituted nitrogen atom, that can be a part of a heterocyclic ring;n is 0, 1 or 2R6 and R.sub.10, that can be the same or different, are: hydrogen; C.sub.1 -C.sub.6 -alkyl optionally substituted by hydroxy, amino, monoalkyl and dialkylamino, C.sub.1 -C.sub.6 -alkoxy, C.sub.1 -C.sub.6 -alkoxycarbonyl, C.sub.1 -C.sub.3 -carbonyloxy, aryl, heteroaryl and cycloalkyl; a C.sub.1 -C.sub.12 -alkanoyl, aroyl or heteroaryl group optionally substituted by halogen, nitro, amino monoalkylamino, dialkylamino, hydroxy, C.sub.1 -C.sub.6 -alkoxy, C.sub.1 -C.sub.6 -alkoxycarbonyl, C.sub.1 -C.sub.6 -alkylthio, C.sub.1 -C.sub.3 -carbonyloxy, aryl, heteroaryl, cycloalkyl groups.