Fused bicyclic-substituted amines as histamine-3 receptor ligands

1. A compound of the formula:

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

X is NH or N(alkyl);

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

Z is N;

one of R 1 and R 2 is heteroaryl;

the other of R 1 and R 2 is selected from the group consisting of hydrogen, alkyl, alkoxy, aryl, cycloalkyl, halo, cyano, and thioalkoxy;

R 3 is absent when Z is N;

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; or one of the pair R 7 and R 8 or the pair R 9 and R 10 is taken together to form a C 3 -C 6 ring, wherein 0, 1, or 2 heteroatoms selected from O, N, or S replace a carbon atom in the ring;

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 when R 1 or R 2 is heteroaryl, 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, 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.

3. 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 —.

4. 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, fluoroalkyl, and hydroxyalkyl.

5. The compound of claim 1 , wherein R 4 and R 5 taken together with the nitrogen atom to which each is attached form a non-aromatic ring that is selected from the group consisting of methylpyrrolidinyl, ethylpyrrolidinyl, dimethylaminopyrrolidinyl, isopropylpyrrolidinyl, isobutylpyrrolidinyl, hydroxymethylpyrrolidinyl, and fluoromethylpyrrolidinyl.

6. 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 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.

7. The compound of claim 1 selected from the group consisting of 2-[2-(2-(R)-Methyl-pyrrolidin-1-yl)-ethyl]-5-pyridin-3-yl-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-(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;

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; and

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

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

9. A compound that is 5-(2,6-difluoro-pyridin-3-yl)-2-[2-(2-(R)-methyl -pyrrolidin- 1-yl)-ethyl]-1H-benzoimidazole or a salt thereof.

10. A compound that is 5-(2,6-dimethyl-pyridin-3-yl)-2-[2-(2-(R)-methyl -pyrrolidin-1-yl)-ethyl]-1H-benzoimidazole or a salt thereof.