The invention relates to antibacterial compounds of formula I wherein R1a represents H or carboxy and R1b represents H, or R1a and R1b represent together either the group *-C(O)-NH-S-# or the group *-C(OH)=N-S-# wherein “*” represents the point of attachment of R1a and “#” represents the point of attachment of R1b； R2 represents H, (C1-C3)alkyl, hydroxy-(C1-C3)alkyl, benzyl or (C3-C5)cycloalkyl； R3 represents H or halogen； U represents N or CR4； wherein R4 is H or (C1-C3)alkoxy； A represents CH, B represents NH and m represents 1 or 2 and n represents 1 or 2； or A represents N, B is absent, m represents 2 and n represents 2； Y represents CH or N； and Q represents O or S； and salts of such compounds.本發明係關於式I之抗細菌化合物其中R1a代表H或羧基且R1b代表H，或R1a及R1b一起代表基團*-C(O)-NH-S-#或基團*-C(OH)=N-S-#，其中「*」代表R1a之附接點且「#」代表R1b之附接點；R2代表H、(C1-C3)烷基、羥基-(C1-C3)烷基、苄基或(C3-C5)環烷基；R3代表H或鹵素；U代表N或CR4；其中R4係H或(C1-C3)烷氧基；A代表CH，B代表NH且m代表1或2且n代表1或2；或A代表N，B不存在，m代表2且n代表2；Y代表CH或N；且Q代表O或S；及該等化合物之鹽。
