A compound of formula I is provided having the structure ##STR00001## wherein W is as defined herein; X is --CHR.sup.5O--; Y is a bond; Z is an aryl or heteroaryl group; and R.sup.1, and R.sup.2, are as described herein. Further provided is a method for treating diabetes and related diseases employing the above compound, either alone or in combination with another therapeutic agent.