The present invention relates to a compound of the formula 1 ##STR00001## wherein R.sup.1-R.sup.4 and Ar are as defined herein. Such novel pyrimidine derivatives are useful in the treatment of abnormal cell growth, such as cancer, in mammals. This invention also relates to a method of using such compounds in the treatment of abnormal cell growth in mammals, especially humans, and to pharmaceutical compositions containing such compounds.