Compounds according to formula I: ##STR00001## wherein R.sup.1, W, R.sup.2, R.sup.3, X, R.sup.4 and R.sup.5 are as described in the specification, enantiomers thereof, pharmaceutically acceptable salts thereof, processes for preparing them, pharmaceutical compositions containing them and their use in therapy, especially for treatment of conditions associated with reductions in nicotinic transmission.