A compound having structural Formula I: and the pharmaceutically acceptable salts thereof wherein: Z 1 is wherein the dashed line represents an optional double bond; Z2 is R 1 is -H, -CH 3, -CF 3, -CHF 2, -CH 2 F or -CH 2 OH; R2 is -H, oxo or -C 1-6 alkyl; R4 is -H, -OH, oxo, -F or -C 1-6 alkyl; provided that when R 4 is -OH, oxo or -F, then R 2 is not oxo; R 6 is -H, -OH, oxo, -F or -C 1-6 alkyl; R 8 is -H, oxo or -C 1-6 alkyl; provided that when R 6 is -OH, oxo or -F, then R 8 is not oxo; R 3, R 5, R 7, and R 9 are each independently -H or -C 1-6 alkyl; provided that R 3 is absent when R 2 is oxo, R 5 is absent when R 4 is oxo, R 7 is absent when R6 is oxo, and R 9 is absent when R 8 is oxo; R 1a is -H, halo or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 1b and R 1c is -CN, -NO 2 or tetrazolyl, and the other is -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 1d, R 1e and R 1f is -CN, -NO 2 or tetrazolyl, and each of the others is independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of-F; R 2a is -H, halo or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 2b and R 2c is -CN, -NO 2 or tetrazolyl, and the other is -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 2d, R 2e and R 2f is -CN, -NO 2 or tetrazolyl, and each of the others is independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of-F; and R a and R b are each independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F. Z 1 is wherein the dashed line represents an optional double bond; Z2 is R 1 is -H, -CH 3, -CF 3, -CHF 2, -CH 2 F or -CH 2 OH; R2 is -H, oxo or -C 1-6 alkyl; R4 is -H, -OH, oxo, -F or -C 1-6 alkyl; provided that when R 4 is -OH, oxo or -F, then R 2 is not oxo; R 6 is -H, -OH, oxo, -F or -C 1-6 alkyl; R 8 is -H, oxo or -C 1-6 alkyl; provided that when R 6 is -OH, oxo or -F, then R 8 is not oxo; R 3, R 5, R 7, and R 9 are each independently -H or -C 1-6 alkyl; provided that R 3 is absent when R 2 is oxo, R 5 is absent when R 4 is oxo, R 7 is absent when R6 is oxo, and R 9 is absent when R 8 is oxo; R 1a is -H, halo or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 1b and R 1c is -CN, -NO 2 or tetrazolyl, and the other is -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 1d, R 1e and R 1f is -CN, -NO 2 or tetrazolyl, and each of the others is independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of-F; R 2a is -H, halo or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 2b and R 2c is -CN, -NO 2 or tetrazolyl, and the other is -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F; one of R 2d, R 2e and R 2f is -CN, -NO 2 or tetrazolyl, and each of the others is independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of-F; and R a and R b are each independently -H, halo, -O-C 1-3 alkyl, -COOC 1-3 alkyl or -C 1-3 alkyl optionally substituted with one to three of -F.