A compound of formula ##STR00001## wherein R.sub.1 is haloalkyl, alkenyl, phenyl, thienyl, pyridine, benzthiazolyl, chromanyl (1,2-dihydrobenzopyranyl) or (C.sub.6-18)aryl, and R.sub.1 or R.sub.2 independently of each other are substituted (C.sub.4-8)cycloalkyl, a substituted bridged cycloalkyl system, substituted piperidine, substituted tetrahydropyridine, or a substituted bridged heterocyclic system, useful as a pharmaceutical.