The invention provides compounds of formula I: ##STR00001## wherein a, b, c, d, f, W, Q, Y, R.sup.1, R.sup.2, and R.sup.3 are as defined in the specification. The compounds of formula I are muscarinic receptor antagonists. The invention also provides pharmaceutical compositions containing such compounds, processes and intermediates for preparing such compounds and methods of using such compounds to treat pulmonary disorders.