A compound of formula: wherein the ring A is selected from one of the following: R 2 is selected from -CO 2 H, -C (CF 3) 2, -C NHSO 2 aryl, -C NHSO 2 alkyl, when Z is C, R 3 is selected from hydrogen, halogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl or heteroaryl; when Z is O, R 3 is absent; R 4 is selected from hydrogen, alkyl, alkenyl, - mcycloalkyl, - maryl, - mheterocyclyl, - mheteroaryl, -(CH 2) m N HC(=NH)NH 2, -(CH 2) m CONH 2, -(CH 2) m CO 2 H, -(CH 2) m SR 6, -(CH 2) m NH 2 or -(CH 2) m OR 6; R 5 is selected from alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl, heteroaryl or -NHR 7; R 6 is selected from hydrogen, alkyl, cycloalkyl, aryl, heterocyclyl or heteroaryl; R 7 is selected from -C R 8, -C OR 8, -C NHR 8 or -S 2 R 8; R 8 is selected from alkyl, alkenyl, -(CHR 9) p cycloalkyl, -(CHR 9) p cycloalkenyl, -(CHR 9) p aryl, -(CHR 9) p heterocyclyl or -(CHR 9) p heteroaryl; R 9 is selected from hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl or heteroaryl; R 10 is selected from: and n is an integer from 1 to 4; m is 0 or an integer from 1 to 6; and p is 0 or an integer from 1 to 6; wherein each cycloalkyl, cycloalkenyl, aryl, heteroaryl and heterocyclyl group may be optionally substituted with one or more optional substituents selected from the group consisting of C 1-6 alkyl, C 2-6 alkenyl, C 3-6 cycloalkyl, oxo (=O), -OH, -SH, C 1-6 alkylO-, C 2-6 alkenylO-, C 3-6 cycloalkylO-, C 1-6 alkylS-, C 2-6 alkenylS-, C 3-6 cycloalkylS-, -CO 2 H, -CO 2 C 1-6 alkyl, -NH 2, -NH(C 1-6 alkyl), -N(C 1-6 alkyl) 2, -NH(phenyl), -N(phenyl) 2,-CN, -NO 2, -halogen, -CF 3, -OCF 3, -SCF 3, -phenyl, -heterocyclyl, -heteroaryl, -Oheteroaryl,-Oheterocyclyl, -Ophenyl, -C phenyl, -C C 1-6 alkyl; or a pharmaceutically acceptable salt thereof. wherein the ring A is selected from one of the following: R 2 is selected from -CO 2 H, -C (CF 3) 2, -C NHSO 2 aryl, -C NHSO 2 alkyl, when Z is C, R 3 is selected from hydrogen, halogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl or heteroaryl; when Z is O, R 3 is absent; R 4 is selected from hydrogen, alkyl, alkenyl, - mcycloalkyl, - maryl, - mheterocyclyl, - mheteroaryl, -(CH 2) m N HC(=NH)NH 2, -(CH 2) m CONH 2, -(CH 2) m CO 2 H, -(CH 2) m SR 6, -(CH 2) m NH 2 or -(CH 2) m OR 6; R 5 is selected from alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl, heteroaryl or -NHR 7; R 6 is selected from hydrogen, alkyl, cycloalkyl, aryl, heterocyclyl or heteroaryl; R 7 is selected from -C R 8, -C OR 8, -C NHR 8 or -S 2 R 8; R 8 is selected from alkyl, alkenyl, -(CHR 9) p cycloalkyl, -(CHR 9) p cycloalkenyl, -(CHR 9) p aryl, -(CHR 9) p heterocyclyl or -(CHR 9) p heteroaryl; R 9 is selected from hydrogen, alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heterocyclyl or heteroaryl; R 10 is selected from: and n is an integer from 1 to 4; m is 0 or an integer from 1 to 6; and p is 0 or an integer from 1 to 6; wherein each cycloalkyl, cycloalkenyl, aryl, heteroaryl and heterocyclyl group may be optionally substituted with one or more optional substituents selected from the group consisting of C 1-6 alkyl, C 2-6 alkenyl, C 3-6 cycloalkyl, oxo (=O), -OH, -SH, C 1-6 alkylO-, C 2-6 alkenylO-, C 3-6 cycloalkylO-, C 1-6 alkylS-, C 2-6 alkenylS-, C 3-6 cycloalkylS-, -CO 2 H, -CO 2 C 1-6 alkyl, -NH 2, -NH(C 1-6 alkyl), -N(C 1-6 alkyl) 2, -NH(phenyl), -N(phenyl) 2,-CN, -NO 2, -halogen, -CF 3, -OCF 3, -SCF 3, -phenyl, -heterocyclyl, -heteroaryl, -Oheteroaryl,-Oheterocyclyl, -Ophenyl, -C phenyl, -C C 1-6 alkyl;