The invention relates to compounds of the formula ##STR00001## and to pharmaceutically acceptable salts thereof, wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, n and m are as defined herein. The compounds of formula I are useful in the treatment of hyperproliferative diseases, such as cancer. The invention further relates to processes of making the compounds of formula I and to methods of using such compounds in the treatment of hyperproliferative diseases.