Fused bicyclic-substituted amines as histamine-3 receptor ligands

1. A compound of the formula:

or a pharmaceutically acceptable salt, ester, amide, or prodrug thereof, wherein:

X is O, S, NH, or N(alkyl);

Y, and Y′ are each independently selected from the group consisting of CH, CF, and N;

Z is C or N, provided that when X is O or S, Z is N;

one of R 1 and R 2 is selected from the group consisting of heteroaryl, and heterocycle;

the other of R 1 and R 2 is selected from the group consisting of hydrogen, alkyl, and alkoxy;

R 3 is absent when Z is N and, when present, R 3 is selected from the group consisting of hydrogen, methyl, alkoxy, halo, and cyano;

R 4 and R 5 taken together with the nitrogen atom to which each is attached form a non-aromatic ring of the structure (a):

R 7 , R 8 , R 9 , and R 10 are each independently selected from the group consisting of hydrogen, hydroxyalkyl, fluoroalkyl, and alkyl;

R 11 , and R 12 are each independently selected from the group consisting of hydrogen, hydroxy, hydroxyalkyl, alkyl, and fluoro;

R 13 and R 14 at each occurrence are independently selected from the group consisting of hydrogen, alkyl, and fluoro;

L is —[C(R 15 )(R 16 )] n —;

R 15 and R 16 at each occurrence are independently selected from the group consisting of hydrogen, alkyl, alkoxy, and fluoro;

m is 1; and

n is an integer from 2–3.

2. The compound of claim 1 , wherein R 1 is heteroaryl.

3. The compound of claim 1 , wherein R 1 and R 2 are each independently selected from the group consisting of furyl, imidazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, oxazolyl, nicotinyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridazinonyl, pyridinyl, pyrimidinyl, pyrrolyl, tetrazolyl, thiadiazolyl, thiazolyl, thienyl, triazinyl, triazolyl, azepanyl, azetidinyl, aziridinyl, azocanyl, morpholinyl, piperazinyl, piperidinyl, pyrrolidinyl, pyrrolinyl, thiomorpholinyl, tetrahydrofuryl, tetrahydropyranyl, benzothienyl, isoquinolyl, indolyl, indolizin-2-yl, indazolyl, imidazo[1,2-a]pyridin-2-yl, pyrazolo[1,5-a)pyridin-2-yl, 3-oxo-2H-pyridazin-2-yl, quinolyl, and 2-oxo-1H-pyridin-1-yl.

4. The compound of claim 1 , wherein R 1 is selected from the group consisting of substituted pyridine, and unsubstituted pyridine.

5. The compound of claim 1 , wherein R 1 is selected from the group consisting of nicotinyl, pyridinyl, and quinolyl.

6. The compound of claim 1 , wherein L is selected from the group consisting of —CH 2 CH 2 — or —CH 2 CH 2 CH 2 —.

7. The compound of claim 1 , wherein R 3 is hydrogen or methyl.

8. The compound of claim 1 , wherein at least one substituent represented by R 7 , R 8 , R 9 , and R 10 is selected from the group consisting of alkyl, halo, fluoroalkyl, and hydroxyalkyl.

9. The compound of claim 1 , wherein the non-aromatic ring of structure (a) is selected from the group consisting of methylpyrrolidinyl, ethylpyrrolidinyl, dimethylaminopyrrolidinyl, isopropylpyrrolidinyl, isobutylpyrrolidinyl, hydroxymethylpyrrolidinyl, and fluoromethylpyrrolidinyl.

10. The compound of claim 1 , wherein at least one substituent represented by R 7 , R 8 , R 9 , and R 10 is hydroxyalkyl, fluoroalkyl, or alkyl.

11. The compound of claim 1 , wherein one substituent represented by R 7 , R 8 , R 9 , and R 10 is methyl, ethyl, fluoromethyl, or hydroxymethyl.

12. The compound of claim 1 , wherein one substituent represented by R 7 , R 8 , R 9 , and R 10 is alkyl and the other three substituents are hydrogen.

13. The compound of claim 1 , wherein R 11 , R 12 , R 13 , and R 14 are each hydrogen.

14. The compound of claim 1 , wherein R 13 and R 14 at each occurrence are each independently selected from the group consisting of hydrogen and alkyl.

15. The compound of claim 1 , wherein R 15 and R 16 are hydrogen.

16. The compound of claim 1 , wherein n is 2.

17. The compound of claim 1 , wherein:

R 1 is heteroaryl;

R 2 and R 3 are hydrogen;

L is —CH 2 CH 2 —;

m is 1; and

R 4 and R 5 are taken together to form a pyrrolidinyl ring of formula (a), wherein one of R 7 , R 8 , R 9 , and R 10 is methyl and the remaining three substituents are hydrogen.

18. The compound of claim 1 selected from the group consisting of

4-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-5-yl}-benzonitrile;

3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-5-yl}-benzonitrile;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-p-tolyl-benzothiazole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-m-tolyl-benzothiazole;

5-(4-Chloro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

5-(3-Chloro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

5-(4-Ethyl-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

Dimethyl-(4-{2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-5-yl}-phenyl)-amine;

5-(4-Fluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

5-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-5-yl}-nicotinonitrile;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-6-pyridin-3-yl-benzothiazole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-6-pyridin-4-yl-benzothiazole;

6-(6-Methoxy-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

6-(3-Chloro-pyridin-4-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

6-(2,6-Difluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

2-Methyl-2′-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-[5,6′]bibenzothiazolyl;

3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-6-yl}-quinoline;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-6-pyrimidin-5-yl-benzothiazole;

6-(6-Fluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

5-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-benzothiazol-6-yl}-nicotinonitrile;

6-(1-Methyl-1H-indol-5-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

6-(2,6-Dimethyl-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole;

4-{2-[2-(2-methyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-[2-(2-Pyrrolidin-1-yl-ethyl)-benzooxazol-5-yl]-benzonitrile;

4-{2-[2-(2-(S)-methyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(3-(R)-Hydroxy-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(S)-Hydroxymethyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(R),5-(R)-Dimethyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-[2-(2-Piperidin-1-yl-ethyl)-benzooxazol-5-yl]-benzonitrile;

4-{2-[2-(2-(R)-methyl-piperidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(S)-Methoxymethyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-[2-(2-Azepan-1-yl-ethyl)-benzooxazol-5-yl]-benzonitrile;

4-[2-(2-Diethylamino-ethyl)-benzooxazol-5-yl]-benzonitrile;

4-{2-[2-(isopropyl-methyl-amino)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(tert-Butyl-methyl-amino)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(Butyl-methyl-amino)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-Hydroxymethyl-piperidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-(2-{2-[2-(2-Hydroxy-ethyl)-piperidin-1-yl]-ethyl}-benzooxazol-5-yl)-benzonitrile;

4-{2-[2-(2-Isopropyl-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(R)-Methyl-azetidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(S)-Fluoromethyl-azetidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(S)-Hydroxymethyl-azetidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-[2-(2-Azetidin-1-yl-ethyl)-benzooxazol-5-yl]-benzonitrile;

4-(2-{2-[cis-2,6-dimethyl-piperidin-1-yl]-ethyl}-benzooxazol-5-yl)-benzonitrile;

4-(2-{2-[1,4,5,6-tetrahydropyrimidin-1-yl]-ethyl}-benzooxazol-5-yl)-benzonitrile;

4-(2-{2-[ethyl-isopropyl-amino]-ethyl}-benzooxazol-5-yl)-benzonitrile;

4-{2-[2-(2-(2-methyl-propyl)-pyrrolidin-1-yl)-ethyl]-benzooxazol-5-yl}-benzonitrile;

4-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-benzonitrile;

4-{1-Methyl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-benzonitrile;

3-{1-Methyl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-benzonitrile;

3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-benzonitrile;

5-(4-Fluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(3,5-Difluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-(4-trifluoromethoxy-phenyl)-1H-indole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-pyridin-3-yl-1H-indole;

1-(3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-phenyl)-ethanone;

5-Furan-2-yl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(2,6-Difluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(6-Methoxy-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(4-Methanesulfonyl-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(2,6-Dimethyl-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

1-(4-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-phenyl)-ethanone;

5-(3-Fluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

Dimethyl-(4-{2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-phenyl)-amine;

5-(4-Chloro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(2,4-Dimethoxy-pyrimidin-5-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-(3-trifluoromethyl-phenyl)-1H-indole;

2-Methyl-5-{2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-benzothiazole;

8-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-quinoline;

5-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-nicotinonitrile;

5-(5-Methoxy-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

5-(6-Fluoropyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-pyrimidin-5-yl-1H-indole;

1-Methyl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-5-pyridin-3-yl-1H-indole;

1-Methyl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-5-pyrimidin-5-yl-1H-indole;

5-{1-Methyl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-indol-5-yl}-nicotinonitrile;

4-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-benzonitrile;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-pyridin-3-yl-1H-benzoimidazole;

5-(4-Fluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

1-(4-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-phenyl)-ethanone;

3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-benzonitrile;

1-(3-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-phenyl)-ethanone;

5-(3-Methoxy-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-Furan-2-yl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(2,6-Difluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(6-Methoxy-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(4-Methanesulfonyl-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(2,4-Dimethoxy-pyrimidin-5-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-Benzo[1,3]dioxol-5-yl-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(5-Methoxy-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

5-(2,6-Dimethyl-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

4-{2-[2-(2-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-benzoic acid methyl ester;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-(4-methylsulfanyl-phenyl)-1H-benzoimidazole;

5-(3,5-Difluoro-phenyl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole;

2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-pyrimidin-5-yl-1H-benzoimidazole;

8-{2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-quinoline;

Dimethyl-(4-{2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazol-5-yl}-phenyl)-amine; and

5-(6-Fluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl-pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole.

19. A pharmaceutical composition comprising a therapeutically effective amount of a compound of claim 1 in combination with a pharmaceutically acceptable carrier.