The present invention includes compounds represented by the formula: ##STR1## wherein X is O or S; R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, hydroxy, halo, loweralkoxy, thioalkoxy and loweralkyl; or R.sub.1 and R.sub.2 taken together can form a methylenedioxy or ethylenedioxy bridge;R.sub.3 is loweralkyl;R.sub.4 is selected from ##STR2## wherein Y is O or S, R.sub.6 is hydrogen, methoxy or halo and m is 0 or 1; R.sub.5 is hydrogen, loweralkyl, phenyl or substituted phenyl wherein the phenyl ring is substituted with one, two or three substituents independently selected from loweralkyl, halo, hydroxy, loweralkoxy, amino and thioalkoxy; andR.sub.8 hydrogen or R.sub.3 and R.sub.8 taken together form a pyrrolidine ring; or a pharmaceutically acceptable salt thereof.