Compounds of the general formula (I) ##STR00001## wherein R.sup.1 represents halogen, R.sup.2 and R.sup.3 represent H or halogen, and R.sup.4 represents C.sub.3-8-cycloalkyl or optionally substituted phenyl, pharamceutical compositions containing such materials, and methods of using such materials in the treatment of various diseases are disclosed and claimed.