Abstract: The present invention relates to certain compounds of the formula (I), ##STR1## which are useful in the synthesis of certain .beta.-adrenergic receptor agonists. The invention also relates to a process for synthesizing the compounds of formula (I) and to compounds of the formula (II), ##STR2## wherein R.sup.1, R.sup.2 and R.sup.4 are defined herein, which are useful in the synthesis of the compounds of formula (I). The invention also relates to a process for synthesizing a compound of formula (II). The invention further relates to processes for synthesizing compounds of formula (Z*), ##STR3## R.sup.1, R.sup.2 and Y.sup.2* are defined herein.