The present invention is directed to compounds represented by the following structural formula, and pharmaceutically acceptable salts thereof, Formula I. (Formula I); wherein: (a) R5 is selected from the group consisting of (C.sub.1 C.sub.6)alkyl, (C.sub.1 C.sub.6)alkenyl, aryl (C.sub.0 C.sub.4)alkyl, aryloxy(C.sub.0 C.sub.4)alkyl, arylthio(C.sub.0 C.sub.4)alkyl, and further wherein when R5 is alkyl, R5 can optionally combine with W to form a 6 membered cycloheteroalkyl ring that is fused with the oxazole or thiazole ring to which the R5 group is attached; (b) R9 is selected from the group consisting of C.sub.1 C.sub.5alkyl, C.sub.1 C.sub.5alkenyl, and arylC.sub.0 C.sub.3alkyl. (c) T.sub.1 is selected from the group consisting of C and N, (d) W is selected from the group consisting of CH.sub.2, C(O)N(R21), N(R21), N(R21)CH.sub.2, O, OCH.sub.2, S, and SO.sub.2; and (e) X is selected from the group consisting of C, CH.sub.2C, and CCH.sub.2 ##STR00001##