The present invention relates to certain compounds of the formula (I) the racemic-enantiomeric mixtures and optical isomers of said compounds and the pharmaceutically acceptable salts or prodrugs thereof, depicted below, which are beta -adrenergic receptor agonists and accordingly have utility as, inter alia, hypoglycemic and antiobesity agents. More specifically, the compounds of the instant invention are selective agonists of beta 3-adrenergic receptor. The invention also relates to methods of use for the compounds and to pharmaceutical compositions containing them. The compounds of the present invention also possess utility for increasing lean meat deposition and/or improving the lean meat to fat ratio in animals, e.g., ungulate animals, companion animals and poultry. The compounds have the formula wherein R, R, R, R, R, Y and Z are as defined in the specification.