Compounds of the formula I: ##STR00001## or pharmaceutically acceptable salts, solvates or prodrugs thereof, wherein m, n, p, Ar, X, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined herein. Also provided are compositions comprising, methods of preparing, and methods of using the subject compounds.