Piperidine derivatives and their use as therapeutic agents

A compound of the formula (I), or a pharmaceutically acceptable salt or prodrug thereof:

• ##STR14## wherein Q represents a phenyl group substituted by one or more halo, optionally substituted naphthyl, optionally substituted indolyl, optionally substituted benzthiophenyl, optionally substituted benzofuranyl, optionally substituted benzyl, or optionally substituted fluorenyl;
• wherein the optional substituents are selected from C.sub.1-6 alkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl, halo, cyano, nitro, trifluoromethyl, trimethylsilyl, OR.sup.a, SR.sup.a, SOR.sup.a, SO.sub.2 R.sup.a, NR.sup.a R.sup.b, NR.sup.a COR.sup.b, NR.sup.a CO.sub.2 R.sup.b, CO.sub.2 R.sup.a or CONR.sup.a R.sup.b, where R.sup.a and R.sup.b are as defined below;
• and where Q is optionally substituted indolyl, the nitrogen substituent is selected from C.sub.1-6 alkyl, optionally substituted phenyl(C.sub.1-4 alkyl), CO.sub.2 R.sup.a or CONR.sup.a R.sup.b, where R.sup.a and R.sup.b are as defined below;
• R.sup.1 represents H, OH, C.sub.1-6 alkoxy or phenyloxy;
• R.sup.2 represents H, C.sub.1-6 alkyl or C.sub.2-6 alkenyl;
• Z represents a group selected from ##STR15## where one of X and Y represents H and the other represents hydroxy or C.sub.1-6 alkoxy, or X and Y together form a group .dbd.O or .dbd.NOR.sup.5 where R.sup.5 is H or C.sub.1-6 alkyl;
• R.sup.3 represents phenyl optionally substituted by 1, 2 or 3 groups selected from C.sub.1-6 alkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl, C.sub.3-7 cycloalkyl, C.sub.3-7 cycloalkylC.sub.1-4 alkyl, halo, cyano, nitro, trifluoromethyl, trimethylsilyl, OR.sup.a, SR.sup.a, SOR.sup.a, NR.sup.a R.sup.b, NR.sup.a COR.sup.b, NR.sup.a CO.sub.2 R.sup.b, CO.sub.2 R.sup.a or CONR.sup.a R.sup.b, where R.sup.a and R.sup.b independently represent H, C.sub.1-6 alkyl, phenyl or trifluoromethyl;
• R.sup.4 represents H or C.sub.1-6 alkyl;
• the dotted line represents an optional covalent bond;
• Ar represents phenyl optionally substituted by 1 or 2 groups selected from C.sub.1-6 alkyl, C.sub.1-6 alkoxy, halo or tirfluoromethyl, and
• n represents zero, 1 or 2.