Polycyclic heterocyclic compounds, a process for their preparation and their use in human and veterinary medicine

A polycyclic heterocyclic compound having the formula ##STR13## wherein n is 1 or 2,

• R.sub.1 represents (i) hydrogen, (ii) --CH.sub.2 OH or (iii) ##STR14## R.sub.2 represents (a) hydrogen, (b) ##STR15## or (c) --OR.sub.3 wherein R.sub.3 represents hydrogen, alkyl having 1-20 carbon atoms, monohydroxyalkyl, polyhydroxyalkyl, phenyl, phenyl substituted by halogen, hydroxy, nitro or lower alkyl, benzyl, phenethyl, a sugar radical selected from the group consisting of glucose, mannose, erythrose and galactose, or ##STR16## wherein p is 1, 2 or 3 and r' and r" represents hydrogen, lower alkyl, monohydroxyalkyl, polyhydroxyalkyl, phenyl, phenyl substituted by halogen, hydroxy, nitro or lower alkyl, aminated sugar radical selected from the group consisting of glucosamine, galactosamine and mannosamine, or r' and r" taken together form a heterocycle selected from the group consisting of piperidino, piperazino, morpholino, pyrrolidino and 4-(2'-hydroxyethyl) piperazino,
• X represents oxygen,
• Y represents a nitrogen atom, or a salt of said polycyclic heterocyclic compound of formula I.