This invention provides compounds of formula I: ##STR00001## wherein a, b, c, e, m, n, Ar.sup.1, R.sup.1, R.sup.2, R.sup.3, R.sup.4a, R.sup.4b, R.sup.5 and R.sup.6 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.