Cephem compound having pyridinium group

A compound of the formula:

• or an amino-protected compound when the amino group is present on the ring in the 7-side chain, or a pharmaceutically acceptable salt thereof,
• wherein
• W is —CH2—, —S— or —O—;
• a) U is —CH2—, —S—, —S(═O)— or —O— when W is —CH2—;
• or
• b) U is —CH2— when W is —S— or —O—;
• L is a single bond, an optionally substituted lower alkylene group, an optionally substituted lower alkenylene group or an optionally substituted alkynylene group;
• R1 is an optionally substituted carbocyclic group or an optionally substituted heterocyclic group;
• with regard to R2A and R2B,
• a) R2A is a hydrogen atom, an optionally substituted amino group, —SO3H, an optionally substituted amino sulfonyl group, carboxyl group, an optionally substituted (lower alkyl)oxycarbonyl group, an optionally substituted carbamoyl group, hydroxyl group, or a substituted carbonyloxy group;
• and R2B is a hydrogen atom, or
• b) R2A and R2B are taken together to form an optionally substituted methylidene group or an optionally substituted hydroxyimino group;
• R3 is a hydrogen atom, —OCH3 or —NH—CH(═O);
• R11 is a bioisoster of carboxyl ion;
• ring E is an optionally substituted pyridinium ring or an optionally substituted fused ring containing pyridinium ring;
• 1) when two hydroxyl groups bind to two adjacent carbon atoms respectively on an aromatic ring of the ring E, R10 is —R12 or a group represented by the formula:
• wherein
• ring A is a benzene ring, or a 6-membered aromatic heterocyclic group having 1-3 nitrogen atoms;
• k is an integer from 2 to 5;
• each R4 is independently a hydrogen atom, halogen, hydroxyl group, —CN, —C(═O)—R5, —C(═O)—OH, —C(═O)—OR5, or —OR5;
• R5 is a lower alkyl group or halo(lower)alkyl group;
• and
• G is a single bond, an optionally substituted lower alkylene group, an optionally substituted alkenylene group or an optionally substituted alkynylene group;
• M is a single bond or a 5- or 6-membered heterocyclic group containing at least 1-3 nitrogen atoms;
• D is a single bond, —CO—, —O—CO—, —CO—O—, —NR6—, —NR6—CO—, —CO—NR6—, —NR6—CO—NR6—, —O—, —S—, —SO—, —SO2—NR6—, —NR6—SO2—, —CH2—NR6—CO— or —SO2—;
• each R6 is independently a hydrogen atom or an optionally substituted lower alkyl group;
• or
• 2) In cases other than the case that two hydroxyl groups bind to two adjacent carbon atoms respectively on an aromatic ring of the ring E,
• R10 is a group represented by the formula:
• wherein
• each symbol is as defined above with the proviso that at least two R4 are hydroxyl groups which bind respectively to adjacent carbon atoms on ring A;
• R12 is a hydrogen atom, halogen, hydroxyl group, —SO3H, an optionally substituted amino group, an optionally substituted carboxyl group, an optionally substituted carbamoyl group, an optionally substituted acyl group, an optionally substituted amino sulfonyl group, an optionally substituted lower alkyl group, an optionally substituted lower alkenyl group, an optionally substituted lower alkynyl group, an optionally substituted non-aromatic carbocyclic group or an optionally substituted non-aromatic heterocyclic group.