Tricyclic compounds as antibacterials

A compound of formula (I) or a pharmaceutically acceptable salt thereof:

• wherein:
• Z is CH or N;
• R1a and R1b are independently selected from hydrogen;
• halogen;
• cyano;
• (C1-6)alkyl;
• (C1-6)alkylthio;
• trifluoromethyl;
• trifluoromethoxy;
• carboxy;
• hydroxy optionally substituted with (C1-6)alkyl or (C1-6)alkoxy-substituted(C1 -6)alkyl;
• (C1 -6)alkoxy-substituted(C1-6)alkyl;
• hydroxy (C1-6)alkyl;
• an amino group optionally N-substituted by one or two (C1-6)alkyl, formyl, (C1-6)alkylcarbonyl or (C1-6)alkylsulphonyl groups;
• and aminocarbonyl wherein the amino group is optionally substituted by (C1-4)alkyl;
• R2 is hydrogen, or (C1-4)alkyl, or together with R6 forms Y as defined below;
• A is a group (ia) or (ib):
• in which:
• R3 is as defined for R1a or R1b or is oxo and n is 1 or 2:
• or A is a group (ii)
• W1, W2 and W3 are CR4R8
• or W2 and W3 are CR4R8 and W1 represents a bond between W3 and N.
• X is O, CR4R8, or NR6;
• one R4 is as defined for R1a and R1b and the remainder and R8 are hydrogen or one R4 and R8 are together oxo and the remainder are hydrogen;
• R6 is hydrogen or (C1-6)alkyl;
• or together with R2 forms Y;
• R7 is hydrogen;
• halogen;
• hydroxy optionally substituted with (C1-6)alkyl;
• or (C1-6alkyl;
• Y is CR4R8CH2;
• CH2CR4R8;
• (C═O);
• CR4R8;
• CR4R8(C═O);
• or (C═O)CR4R8;
• or when X is CR4R8, R8 and R7 together represent a bond;
• R5 is a group —X1a—X2a—X3a—X4a in which:
• X1a is CH2, CO or SO2;
• X2a is CR14aR15a;
• X3a is NR13a;
• O, S, SO2 or CR14aR15a;
• wherein:
• each of R14a and R15a is independently selected from:
• H;
• (C1-4)alkylthio;
• halo;
• carboxy(C1-4)alkyl;
• halo(C1-4)alkoxy;
• halo(C1-4)alkyl;
• (C1-4)alkyl;
• (C2-4)alkenyl;
• (C1-4)alkoxycarbonyl;
• formyl;
• (C1-4)alkylcarbonyl;
• (C2-4)alkenyloxycarbonyl;
• (C2-4)alkenylcarbonyl;
• (C1-4)alkylcarbonyloxyl ;
• (C1- 4)alkoxycarbonyl(C1-4)alkyl;
• hydroxy;
• hydroxy(C1-4)alkyl;
• mercapto(C1-4)alkyl;
• (C1-4)alkoxy;
• nitro;
• cyano;
• carboxy;
• amino or aminocarbonyl optionally substituted as for corresponding substituents in R3;
• (C1-4)alkylsulphonyl;
• (C2-4)alkenylsulphonyl;
• or aminosulphonyl wherein the amino group is optionally substituted by (C1-4)alkyl or (C2-4)allcenyl;
• aryl;
• aryl(C1-4)alkyl;
• aryl(C1-4)alkoxy;
• provided that R14a and R15a on the same carbon atom are not both selected from optionally substituted hydroxy and optionally substituted amino;
• or
• R14a and R15a together represent oxo;
• R13a is hydrogen;
• trifluoromethyl;
• (C1-6)allcyl;
• (C2-6)alkenyl;
• (C1-6)alkoxycarbonyl;
• (C1-6)alkylcarbonyl;
• or aminocarbonyl wherein the amino group is optionally substituted by (C1-6)alkoxycarbonyl, (C1-6)alkylcarbonyl, (C2-6)alkenyloxycarbonyl, (C2-6)alkenylcarbonyl, (C1-6)alkyl or (C2-6)alkenyl and optionally further substituted by (C1-6)alkyl or (C2-6)alkenyl;
• or
• two R14a groups or an R13a and an R14a group on adjacent atoms together represent a bond and the remaining R13a, R14a and R15a groups are as above defined;
• or
• two R14a groups and two R15a groups on adjacent atoms together represent bonds such that X2a and X3a is triple bonded;
• X4a is phenyl or C or N linked monocyclic aromatic 5- or 6-membered heterocycle containing up to four heteroatoms selected from O, S and N and:
• optionally C-substituted by up to three groups selected from (C1-4)alkylthio;
• halo;
• carboxy(C1-4)alkyl;
• halo(C1-4)alkoxy;
• halo(C1-4)alkyl;
• (C1-4)alkyl;
• (C2-4)alkenyl;
• (C1-4)allcoxycarbonyl;
• formyl;
• (C1-4)alkylcarbonyl;
• (C2-4)alkenyloxycarbonyl;
• (C2-4)alkenylcarbonyl;
• (C1-4)alkylcarbonyloxy;
• (C1-4)alkoxycarbonyl(C1-4)alkyl;
• hydroxy;
• hydroxy(C1-4)alkyl;
• mercapto(C1-4)alkyl;
• (C1-4)alkoxy;
• nitro;
• cyano;
• carboxy;
• amino or aminocarbonyl optionally substituted as for corresponding substituents in R3;
• (C1-4)alkylsulphonyl;
• (C2-4)alkenylsulphonyl;
• or aminosulphonyl wherein the amino group is optionally substituted by (C1-4)alkyl or (C2-4)alkenyl;
• aryl, aryl(C1-4)alkyl or aryl(C1-4)allcoxy;
• and
• optionally N substituted by trifluoromethyl;
• (C1-4)alkyl optionally substituted by hydroxy, (C1-6)alkoxy, (C1-6)alkylthio, halo or trifluoromethyl;
• (C2-4)alkenyl;
• aryl;
• aryl(C1-4)alkyl;
• (C1-4)alkoxycarbonyl;
• (C1-4)alkylcarbonyl;
• formyl;
• (C1-6)alkylsulphonyl;
• or aminocarbonyl wherein the amino group is optionally substituted by (C1-4)alkoxycarbonyl, (C1-4)alkylcarbonyl, (C2-4)alkenyloxycarbonyl, (C2-4)alkenylcarbonyl, (C1-4)alkyl or (C2-4)alkenyl and optionally further substituted by (C1-4)alkyl or (C2-4)alkenyl;
• and
• R9 is hydrogen or hydroxy, or when Z is N R9 may instead be fluoro.