The invention is directed to compounds of formula I: ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7a, R.sup.7b, W, G.sup.1, G.sup.2, a, b, c, d and m are as defined in the specification, or a pharmaceutically acceptable salt or solvate or stereoisomer thereof. The invention is also directed to pharmaceutical compositions comprising such compounds; methods of using such compounds; and process and intermediates for preparing such compounds.