This invention provides compounds of formula I: ##STR00001## wherein a, b, c, m, p, s, t, W, Ar.sup.1, X.sup.1, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.6, and R.sup.7 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.