Compounds are disclosed of formula (I)
wherein
R₁ represents -COR₄, -CO₂R₄, -COCO₂R₄ or -CONR₄R₅(where R₄ and R₅ may be the same or different and represent a hydrogen atom or a C₁₋₃alkyl group);
R₂ represents a hydrogen atom or a hydroxy or oxo group, with the proviso that when R₁ is -COR₄, -CO₂R₄ or -COCO₂R₄, R₂ is not a hydrogen atom;
R₃ represents a hydrogen atom or a hydroxy group;
X represents a direct bond, -CH₂- or -CH₂O-;
Ar represents a substituted phenyl moiety;
and physiologically acceptable salts thereof.
The compounds are indicated as useful in the treatment of pain.
Processes for their preparation and pharmaceutical compositions containing them are also disclosed.