Compounds of the formula ##STR1## and the pharmaceutically acceptable salts thereof, wherein: Y is a direct link, --CH.sub.2 --, --(CH.sub.2).sub.2 --, --CH.sub.2 O-- or --CH.sub.2 S--; R is --CN or --CONH.sub.2 ; and R.sup.1 is ##STR2## where X and X.sup.1 are each independently O or CH.sub.2 ; and m is 1, 2 or 3, are muscarinic receptor antagonists useful in the treatment of diseases and conditions associated with the altered motility and/or tone of smooth muscle, such as irritable bowel syndrome.