The present invention relates to a compound of the formula 1 ##STR00001## or a pharmaceutically acceptable salt, solvate, hydrate, or prodrug thereof, 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 a method of using such compounds in the treatment of abnormal cell growth in mammals, especially humans, and to pharmaceutical compositions containing such compounds.