A compound having structural Formula I and the pharmaceutically acceptable salts thereof wherein: R 1 is -H or -C 1-4 alkyl; X is O, NH or S; Z 1 is R 2 is -H, halo, -C 1-6 alkyl, -C 3-6 cycloalkyl or -OC 1-6 alkyl; R 3 is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; R 4 is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; or R3 and R4 are joined together, and with the phenyl ring to which they are attached together represent: wherein R is -H or -C 1-4 alkyl; R 5 is -H, halo, -CN, -C 1-4 alkyl, -OC 1-4 alkyl or -C 3-6 cycloalkyl; provided that when R3 and R 4 are not joined together, then (a) one and only one of R3, R 4 or R5 is -CN, or (b) one of R3 or R 4 is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; Z 2 is R 2a is -H, halo, -C 1-6 alkyl, -C 3-6 cycloalkyl or -OC 1-6 alkyl; R 3a is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; R 4a is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; or R 3a and R 4a are joined together, and with the phenyl ring to which they are attached together represent: wherein R a is -H or -C 1-4 alkyl; R 5a is -H, halo, -CN, -C 1-4 alkyl, -OC 1-4 alkyl or -C 3-6 cycloalkyl; provided that when R 3a and R 4a are not joined together, then (a) one of R 3a, R 4a or R 5a is -CN and the others are not -CN, or (b) one of R 3a or R 4a is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; R 6 is -H, -OH or -C 1-3 alkyl; or R 6 is -O- and is joined together with Z 2 to represent: R7 is -H; or R7 together with -CHR6- and Z 2 represents R 8 is -H or -C 1-3 alkyl; and R9 is -H or -CH 3. R 1 is -H or -C 1-4 alkyl; X is O, NH or S; Z 1 is R 2 is -H, halo, -C 1-6 alkyl, -C 3-6 cycloalkyl or -OC 1-6 alkyl; R 3 is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; R 4 is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; or R3 and R4 are joined together, and with the phenyl ring to which they are attached together represent: wherein R is -H or -C 1-4 alkyl; R 5 is -H, halo, -CN, -C 1-4 alkyl, -OC 1-4 alkyl or -C 3-6 cycloalkyl; provided that when R3 and R 4 are not joined together, then (a) one and only one of R3, R 4 or R5 is -CN, or (b) one of R3 or R 4 is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; (a) one and only one of R3, R 4 or R5 is -CN, or (b) one of R3 or R 4 is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; Z 2 is R 2a is -H, halo, -C 1-6 alkyl, -C 3-6 cycloalkyl or -OC 1-6 alkyl; R 3a is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; R 4a is -H, halo, -CN, -C 1-6 alkyl, -C 3-6 cycloalkyl, -OC 1-6 alkyl or N-tetrazolyl optionally substituted with -CH 3; or R 3a and R 4a are joined together, and with the phenyl ring to which they are attached together represent: wherein R a is -H or -C 1-4 alkyl; R 5a is -H, halo, -CN, -C 1-4 alkyl, -OC 1-4 alkyl or -C 3-6 cycloalkyl; provided that when R 3a and R 4a are not joined together, then (a) one of R 3a, R 4a or R 5a is -CN and the others are not -CN, or (b) one of R 3a or R 4a is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; (a) one of R 3a, R 4a or R 5a is -CN and the others are not -CN, or (b) one of R 3a or R 4a is N-tetrazolyl optionally substituted with -CH 3 and the other is not N-tetrazolyl optionally substituted with -CH 3; R 6 is -H, -OH or -C 1-3 alkyl; or R 6 is -O- and is joined together with Z 2 to represent: R7 is -H; or R7 together with -CHR6- and Z 2 represents R 8 is -H or -C 1-3 alkyl; and R9 is -H or -CH 3.