Compounds are provided which are useful in treating disorders of gastrointestinal motility and which have the structure ##STR00001## or a pharmaceutically acceptable salt thereof, a prodrug ester thereof, and all stereoisomers thereof, wherein R.sub.1 and R.sub.2 are the same or different and are independently selected from hydrogen, alkyl, aryl, cycloalkyl, alkenyl, alkynyl, arylalkyl, heteroaryl, heteroarylalkyl or heterocycloalkyl; Z is selected from --CON(R.sub.4)R.sub.4a, --CO.sub.2R.sub.4, --SO.sub.2N(R.sub.4)R.sub.4a, --SO.sub.2R.sub.4, CN, and ##STR00002## R.sub.4 and R.sub.4a are the same or different and are independently selected from hydrogen, alkyl, cycloalkyl, aryl, arylalkyl, heteroaryl, or heteroarylalkyl or R.sub.4 and R.sub.4a can be joined together to form a heterocycle. R.sub.4b is selected from hydrogen, halogen, hydroxyl, CN, OCF.sub.3, CF.sub.3, CONH.sub.2, SONH.sub.2, SO.sub.2CH.sub.3, NHCOCH.sub.3 or NHCO.sub.2CH.sub.3; and Q is a substituted bicyclic heterocycle. A method for using such compounds for treating disorders of gastrointestinal motility is also provided.