Pyridine derivatives and pharmaceutical compositions containing them

A compound of formula I:

• ##STR53## wherein;
• X is O, S or CH.sub.2 ;
• R.sup.1 and R.sup.2 are independently hydrogen, C.sub.1-6 alkyl or C.sub.3-6 cycloalkyl or R.sup.1 and R.sup.2 together with the carbon atom to which they are attached form a C.sub.3-6 cycloalkyl group;
• Ar.sup.1 is a fused bicyclic ring system containing one or more heteroatoms, a fused tricyclic ring system optionally containing an oxygen atom, or Ar.sup.1 is a group R.sup.3 --R.sup.4 where one of R.sup.3 /R.sup.4 is a phenyl ring and the other is a 5- or 6-membered heterocyclic ring containing one or more heteroatoms, each Ar.sup.1 group being optionally substituted by halo, nitro, C.sub.1-6 alkyl (optionally substituted by one or more fluorine atoms), CN, --Y--NR.sup.6 C(O)NR.sup.7 --R.sup.8, --O--Y--C(O)NR.sup.7 R.sup.8, --O--Y--C(S)NR.sup.7 R.sup.8, --Y--C(O)NR.sup.7 R.sup.8, --Y--C(S)NR.sup.7 R.sup.8, --Y--SO.sub.2 NR.sup.7 R.sup.8, --Y--NR.sup.7 R.sup.8, SO.sub.2 NR.sup.7 R.sup.8, C(O)NR.sup.7 R.sup.8, C(S)NR.sup.7 R.sup.8, C(O)R.sup.9, --OC(O)R.sup.9, --Y--OR.sup.9, --Y--CO.sub.2 R, --Y--NR.sup.10 C(O)NR.sup.11 --Z--R.sup.12, SO.sub.2 NR.sup.10, C(O)NR.sup.7 R.sup.8, --Y--SO.sub.2 NHNR.sup.7 R.sup.8, --Y--C(O)NR.sup.11 --Z--R.sup.12, --Y--C(S)NR.sup.11 --Z--R.sup.12, N(R.sup.10)SO.sub.2 R.sup.11, N(R.sup.10)C(O)R.sup.11 or N(R.sup.10)CO.sub.2 R.sup.11 where:
• Y is a bond, C.sub.1-6 alkylene or C.sub.2-6 alkenylene;
• R.sup.7 and R.sup.8 are independently hydrogen or C.sub.1-6 alkyl or together with the nitrogen atom to which they are attached form an optionally substituted 5- to 7-membered heterocyclic ring optionally containing a further heteroatom selected from nitrogen, oxygen or sulfur;
• R.sup.5, R.sup.6, R.sup.9, R.sup.11 and R.sup.10 are independently hydrogen or C.sub.1-10 alkyl (optionally substituted by one or more fluorine atoms);
• Z is C.sub.1-6 alkylene;
• and
• R.sup.12 is a group NR.sup.10 C(O)R.sup.11, NR.sup.10 CO.sub.2 R.sup.11, OR.sup.5, NR.sup.7 R.sup.8 or CO.sub.2 R.sup.13 where R.sup.5, R.sup.7, R.sup.8, R.sup.10 and R.sup.11 are as defined above and R.sup.13 is hydrogen, C.sub.1-6 alkyl, C.sub.1-6 alkylaryl or aryl optionally substituted by hydroxy, or a salt or solvate thereof,
• provided that R.sup.4 is not thiazinyl, thiazolyl or alkyl substituted thiazolyl, and
• provided that when R.sup.4 is a pyridyl ring, said ring has one or more substituents as defined above other than alkyl groups.