Cephem derivative

1. A compound of the formula:

or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof,

wherein

W is —CH 2 —, —S—, or —O—; provided that

a) when W is —CH 2 —, then U is —CH 2 —, —S—, or —O—, and

b) when W is —S— or —O—, then U is —CH 2 —;

R 1 is an optionally substituted carbocyclic group, or optionally substituted heterocyclic group;

with regard to R 2A and R 2B ,

a) R 2A is an optionally substituted amino group, —SO 3 H, optionally substituted aminosulfonyl group, carboxyl group, optionally substituted (lower alkyl)oxycarbonyl group, optionally substituted carbamoyl group, hydroxyl group, or a substituted carbonyloxy group; and R 2B is a hydrogen atom, or

b) R 2A and R 2B are taken together to form an optionally substituted alkenyl group, or optionally substituted oxime group,

provided that when R 1 is an aminothiazole of which the amino group is optionally protected, or an aminothiadiazole of which the amino group is optionally protected, R 2A and R 2B are not taken together to form an optionally substituted oxime group;

ring A is a benzene ring, or 6-membered aromatic heterocyclic group having 1-3 nitrogen atoms;

R 3 is a hydrogen atom, —OCH 3 , or —NH—CH(═O);

k is an integer from 0 to 2;

each R 4 is independently a hydrogen atom, halogen, hydroxyl group, —CN, —C(═O)—R 6 , —C(═O)—OH, —C(═O)—OR 6 , or —OR 6 ;

R 6 is a lower alkyl or halo(lower)alkyl; and

with regard to D and E,

a) D is a single bond, —N(R 8 )—, or —R 7 —N(R 8 )— wherein R 7 is an optionally substituted lower alkylene, and R 8 is a hydrogen or lower alkyl; and E is an optionally substituted quaternary ammonium group of the formula selected from the following formula (1) to (40) and (42) to (53), or

b) D has the formula:

wherein q is an integer of 0 or 1, and E has the formula of a quaternary ammonium group represented by the following formula (10) or (41);

wherein p is an integer from 1 to 3; n is an integer of 1 or 2; R X is an optionally substituted lower alkyl; the left side of attachment binds to methylene; and the right side of attachment binds to D, provided that the case where R 1 is a phenyl and E has the formula (53) is excluded.

2. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein D is a single bond, —NH—, or —R 7 —NH— wherein R 7 is as defined in claim 1 .

3. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein D is —NH—, —CH 2 —NH—, or —CH 2 —CH 2 —NH—.

4. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein D is a single bond.

5. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein D has the formula of:

wherein q is as defined in claim 1 .

6. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein E is selected from formula (1) to (9), (11) to (40), (47) to (49), (51) and (52).

7. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein E is selected from formula (5), (6), (9) to (11), (26), (29) to (34), (36), (37) and (50).

8. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein E is selected from formula (5), (6), (10) and (11).

9. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein E is selected from formula (1) to (4), (7), (8), (12) to (25), (27), (28), (35), (38) to (40), (47) and (48).

10. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein E is selected from formula (1) to (3), (7) and (12).

11. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein U is —S—.

12. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein W is —CH 2 —.

13. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein R 3 is a hydrogen atom or —OCH 3 .

14. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein the formula:

is selected from the following:

15. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein the formula:

is selected from the following:

16. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein the formula:

is selected from the following:

17. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein R 1 is an optionally substituted phenyl.

18. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein R 2A is an optionally substituted amino group, —SO 3 H, optionally substituted aminosulfonyl group, carboxyl group, optionally substituted carbamoyl group, hydroxyl group, or substituted carbonyloxy group.

19. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein R 2A is selected from a substituted amino group shown below:

a substituted aminosulfonyl group shown below:

wherein ring B represents an optionally substituted heterocyclic group;

a substituted carbamoyl group shown below:

wherein ring B represents an optionally substituted heterocyclic group; or

a substituted carbonyloxy group shown below:

wherein ring B represents an optionally substituted heterocyclic group.

20. The compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 , wherein R 2A and R 2B are taken together to form a substituted alkenyl group shown below:

or

a substituted oxime group shown below:

wherein R 7 and R 8 are each independently a hydrogen atom, halogen, hydroxy, carboxy, optionally substituted lower alkyl, optionally substituted carbocyclic group, or optionally substituted heterocyclic group, or

R 7 and R 8 may be taken together with a neighboring atom to form an optionally substituted carbocyclic group or optionally substituted heterocyclic group;

R 9 is an optionally substituted lower alkyl; and

m is an integer from 0 to 3.

21. A pharmaceutical composition, which comprises a compound, or an ester, a protected compound at the amino on the ring in the 7-side chain, a pharmaceutically acceptable salt, or a solvate thereof according to claim 1 .

22. The pharmaceutical composition according to claim 21 , which possesses antimicrobial activity.