The invention provides biphenyl derivatives of formula 1: wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , W, a, b and c are as defined in the specification, or a pharmaceutically acceptable salt or solvate or stereoisomer thereof. The biphenyl derivatives of this invention possess both ² 2 adrenergic receptor agonist and muscarinic receptor antagonist activity and therefore, such biphenyl derivatives are useful for treating pulmonary disorders, such as chronic obstructive pulmonary disease and asthma.
