The present invention provides compounds of the formula: ##STR00001## wherein R.sup.1 is C.sub.3-6 cycloalkyl optionally substituted by one or more fluorine atoms, or C.sub.1-6 alkyl optionally substituted by one or more fluorine atoms, or C.sub.3-6 cycloalkylmethyl optionally ring-substituted by one or more fluorine atoms; and R.sup.2 is phenyl optionally substituted by one or more fluorine atoms, to pharmaceutically acceptable salts and solvates thereof, and to processes for the preparation of, intermediates used in the preparation of, compositions containing and the uses of, such compounds.