Tetracyclic piperidine and 1,4-oxazine compounds

A compound selected from those of formula I ##STR38## wherein:

• X represents an oxygen atom or CH.sub.2, and Y represents CH.sub.2
• A-B represents --(CH.sub.2).sub.2 -- or --HC.dbd.CH-- or ##STR39## R represents a hydrogen atom or a (C.sub.1 -C.sub.10)alkyl, (C.sub.3 -C.sub.10)alkenyl, or (C.sub.3 -C.sub.10)alkynyl radical, each of which may be in straight or branched chain and each of which may optionally be substituted by a cycloalkyl radical having 3 to 8 carbon atoms, or by an aryl radical selected from the radicals phenyl, thienyl and pyridyl, each of which may optionally be substituted by one or more substituents selected from halogen atoms, hydroxy radicals, and alkyl and alkoxy radicals each having 1 to 6 carbon atoms in straight or in branched chain;
• and
• n represents:
• 0or 1 when X represents CH.sub.2 and
• 1 only, when X represents an oxygen atom
• their geometric isomer forms, cis and trans,--their racemic mixture or racemate, and their optical isomer or enantiomer forms,
• and their salts with a pharmaceutically-acceptable acid.