Antibacterial compounds

1. A compound having formula (I)

or a salt thereof, in which

R 1 is —OH, —OR 7 , —NH 2 , —NHR 7 , or —N(R 7 ) 2 ;

R 2 is hydrogen or R P , in which R P is —C(CH 3 ) 3 , —O(CH 2 CH═CH 2 ), or (2,4-dimethoxyphenyl)methyl;

R 3 is hydrogen, R 8 , —C(O)R 8 , —C(O)OR 8 , R 9 , —C(O)OCH 2 R 9 , or R 10 ;

R 4 is hydrogen, R 11 , —C(O)R 11 , R 12 , R 13 , R 14 , or R 15 ;

R 5 is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 20a , —F, —Cl, —Br, —I, —OH, —OR 20a , —NO 2 , —NH 2 , —NHR 20a , or —N(R 20a ) 2 substituents; R 20a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 alkyl;

R 6 is hydrogen, R 21 , —OH, —OR 21 , —NH 2 , —NHR 21 , —N(R 21 ) 2 ;

R 7 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl,or C 6 -alkyl;

R 8 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, or R 8a ; R 8a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 8b , —NH 2 , —NHR 8b , —N(R 8b ) 2 , or R 8c substituents; R 8b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 8c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 8d , —F, —Cl, —Br, —I, —OH, —OR 8d , —NO 2 , —NH 2 , —NHR 8d , or —N(R 8d ) 2 substituents; R 8d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 9 is phenyl which is unfused or fused with benzene, cyclopentane, cyclopentene, cyclohexane, or cyclohexene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 9a , —F, —Cl, —Br, —I, —OH, —OR 9a , —NO 2 , —NH 2 , —NHR 9a , or —N(R 9a ) 2 substituents; R 9a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 10 is furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 10a , —F, —Cl, —Br, —I, —OH, —OR 10a , —NO 2 , —NH 2 , —NHR 10a , or —N(R 10a ) 2 substituents; R 10a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 11 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, or R 11a ; R 11a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 11b , —NH 2 , —NHR 11b , —N(R 11b ) 2 or R 11c substituents; R 11b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 11c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 11d , —F, —Cl, —Br, —I, —OH, —OR 11d , —NO 2 , —NH 2 , —NHR 11d , or —N(R 11d ) 2 substituents; R 11d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 12 is C 2 -alkenyl, C 3 -alkenyl, C 4 -alkenyl, C 5 -alkenyl, C 6 -alkenyl, or R 12a ; R 12a is C 2 -alkenyl, C 3 -alkenyl, C 4 -alkenyl, C 5 -alkenyl, C 6 -alkenyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 12b , —NH 2 , —NHR 12b , —N(R 12b ) 2 , or R 12c substituents; R 12b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 12c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 12d , —F, —Cl, —Br, —I, —OH, —OR 12d , —NO 2 , —NH 2 , —NHR 12d , or —N(R 12d ) 2 substituents; R 12d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 13 is C 2 -alkynyl, C 3 -alkynyl, C 4 -alkynyl, C 5 -alkynyl, C 6 -alkenyl, or R 13a ; R 13a is C 2 -alkynyl, C 3 -alkynyl, C 4 -alkynyl, C 5 -alkynyl, C 6 -alkynyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 13b , —NH 2 , —NHR 13b , —N(R 13b ) 2 , or R 13c substituents; R 13b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 13c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 13d , —F, —Cl, —Br, —I, —OH, —OR 13d , —NO 2 , —NH 2 , —NHR 13d , or —N(R 13d ) 2 substituents; R 13d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 14 is C 2 -alkynyl, C 3 -alkynyl, C 4 -alkynyl, C 5 -alkynyl, C 6 -alkenyl, or R 14a ; R 14a is C 2 -alkynyl, C 3 -alkynyl, C 4 -alkynyl, C 5 -alkynyl, C 6 -alkynyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 14b , —NH 2 , —NHR 14b , —N(R 14b ) 2 , or R 14c substituents; R 14b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 14c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 14d , —F, —Cl, —Br, —I, —OH, —OR 14d , —NO 2 , —NH 2 , —NHR 14d , or —N(R 14d ) 2 substituents; R 14d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 15 is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 15a , —F, —Cl, —Br, —I, —OH, —OR 15a , —NO 2 , —NH 2 , —NHR 15a , or —N(R 15a ) 2 substituents; R 15a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 21 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, or R 21a ; R 21a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 21b , —NH 2 , —NHR 21b , —N(R 21b ) 2 , or R 21c substituents; R 21b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 21c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 21d , —F, —Cl, —Br, —I, —OH, —OR 21d , —NO 2 , —NH 2 , —NHR 21d , or —N(R 21d ) 2 substituents; R 21d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

X 1 is —O—;

R 22 is R 23 , —OH, —OR 23 , —C(O)R 23 , —C(O)OR 23 , —C(O)OCH 2 R 24 , —R 25 or —CH 2 R 25 ;

R 23 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, or R 23a ; R 23a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 23b , —NH 2 , —NHR 23b , —N(R 23b ) 2 , or R 23c substituents; R 23b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 23 C is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 23d , —F, —Cl, —Br, —I, —OH, —OR 23d , —NO 2 , —NH 2 , —NHR 23d , or —N(R 23d ) 2 substituents; R 23d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl;

R 24 is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, or R 24a ; R 24a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, C 6 -alkyl, each of which is substituted with one or two or three independently selected —F, —Cl, —Br, —I, —CF 3 , —CF 2 CF 3 , —OH, —OR 24b , —NH 2 , —NHR 24b , —N(R 24b ) 2 , or R 24c substituents; R 24b is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; R 24c is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 24d , —F, —Cl, —Br, —I, —OH, —OR 24d , —NO 2 , —NH 2 , —NHR 24d , or —N(R 24d ) 2 substituents; R 24d is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl; and

R 25 is phenyl, furanyl, imidazolyl, isothiazolyl, isoxazolyl, 1,2,3-oxadiazoyl, oxazolyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridinyl, pyrrolyl, thiazolyl, thiophenyl, triazinyl, or 1,2,3-triazolyl, each of which is unfused or fused with benzene, furan, imidazole, isothiazole, isoxazole, 1,2,3-oxadiazole, oxazole, pyrazine, pyrazole, pyridazine, pyridine, pyrrole, thiazole, or thiophene, in which each ring is independently unsubstituted or substituted with one or two or three independently selected R 25a , —F, —Cl, —Br, —I, —OH, —OR 25a , —NO 2 , —NH 2 , —NHR 25a , or —N(R 25a ) 2 substituents; R 25a is C 1 -alkyl, C 2 -alkyl, C 3 -alkyl, C 4 -alkyl, C 5 -alkyl, or C 6 -alkyl.

2. A compound of claim 1 having formula (I),or a salt thereof,which is

6-(2,4-dimethoxybenzyl)-4-methyl-9-oxo-2-phenyl -3,4,6,9-tetrahydro-2H-[1,4]-oxazino[3,2-b][1,8]naphthyridine -8-carboxylic acid,

4-methyl-9-oxo-2-phenyl-3,4,6,9-tetrahydro-2H -[1,4]-oxazino[3,2-b][1,8]naphthyridine-8-carboxylic acid 6-(2,4-dimethoxybenzyl)-4-methyl-9-oxo-3,4,6,9tetrahydro -2H-[1,4]oxazino[3,2-b][1,8]naphthyridine-8-carboxylic acid or

6-(2,4-dimethoxybenzyl)-4-ethyl-9-oxo-3,4,6,9-tetrahydro-2H-[1,4]-oxazino[3,2-b][1,8]naphthyridine-8-carboxylic acid.

3. A composition for treating bacterial infections in a fish or a mamma 1 ,the compositions comprising a therapeutically effective amount of a compound having formula (I),or a salt thereof,and an excipient.

4. A method for treating bacterial infections in a fish or a mamma 1 ,the method comprising administering thereto a therapeutically effective amount of compound having formula (I),or a salt thereof.