Compounds of formula I, ##STR1## wherein R.sup.1 represents C.sub.1-4 alkoxy optionally substituted by one or more fluorine atoms;R.sup.2 and R.sup.3 independently represent H or C.sub.1-6 alkoxy (which is optionally substituted);R.sup.4 represents a 4-, 5-, 6- or 7-membered heterocyclic ring, the ring being optionally fused to a benzene ring or a 5- or 6-membered heterocyclic, the ring system as a whole being optionally substituted;X represents CH or N; andL is absent,or represents a cyclic group of formula Ia, ##STR2## or represents a chain of formula Ib, ##STR3## and pharmaceutically acceptable salts thereof, are useful in therapy, in particular in the treatment of benign prostatic hyperplasia.