Bicyclic AZA compounds as muscarinic M1 receptor and/or M4 receptor

1. A compound of the formula (1b):

or a salt thereof, wherein

Q is a five membered heterocyclic ring selected from the group consisting of:

R 3 is selected from hydrogen; fluorine; cyano; hydroxy; amino; and a C 1-9 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms and wherein one, two or three, but not all, carbon atoms of the hydrocarbon group may optionally be replaced by a heteroatom selected from O, N and S and oxidized forms thereof;

R 4 is a hydrogen or a C 1-6 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms and wherein one or two, but not all, carbon atoms of the hydrocarbon group may optionally be replaced by a heteroatom selected from O, N and S and oxidised forms thereof;

and the dotted line indicates an optional second carbon-carbon bond, wherein R 3 is present and the optional second carbon-carbon bond is absent.

2. A compound according to claim 1 wherein R 3 is selected from hydrogen; fluorine; hydroxyl, methoxy and cyano.

3. A compound according to claim 1 wherein R 4 is selected from hydrogen and methyl.

4. A pharmaceutically acceptable salt of a compound according to claim 1 which is selected from the group consisting of:

Ethyl 2-[4-(1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4-chloro-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[4-(trifluoromethyl)-1H-imidazol-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4-cyano-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4,5-dichloro-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(ethoxycarbonyl)-1H-imidazol-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1,5-dimethyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,5-dimethyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1,4-dimethyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,4-dimethyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(5-chloro-1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(5-chloro-1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-methyl-4-(trifluoromethyl)-1H-imidazol-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(4,5-dichloro-1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4,5-dichloro-1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4(1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3-amino-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-methyl-1H-pyrazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,3-oxazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1,3-thiazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,3-thiazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4H-1,2,4-triazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(5-ethyl-1H-1,2,4-triazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,3,4-oxadiazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3-methyl-1,2,4-oxadiazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,2,4-thiadiazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-tetrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-pyrrol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4-methyl-1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-1,2,3-triazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-1,2,4-triazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-hydroxy-4-(1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-imidazol-2-yl)-4-methoxypiperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-hydroxy-4-(1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-methoxy-4-(1-methyl-1H-imidazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-methyl-4-(3-methyl-1,2,4-oxadiazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(4-methyl-1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4(1,2-oxazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3-methyl-1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(3-methyl-1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1-ethyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-ethyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1-propyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-propyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,3-thiazol-4-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(2-methoxyethyl)-1H-imidazol-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(cyanomethyl)-1H-imidazol-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

(2-{1-[6-(ethoxycarbonyl)-6-azaspiro[3.4]oct-2-yl]piperidin-4-yl}-1H-imidazol-1-yl)acetic acid;

Ethyl 2-(4-{1-[2-(methylamino)-2-oxoethyl]-1H-imidazol-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1,4-dimethyl-1H-pyrazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,4-dimethyl-1H-pyrazol-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1,4-dimethyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1,4-dimethyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-ethyl-4-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(4-ethyl-1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2H-1,2,3-triazol-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1H-tetrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(5-methyl-1H-tetrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-methyl-1H-tetrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-ethyl-1H-tetrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2-ethyl-2H-tetrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-cyclopropyl-1H-tetrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

(1,1- 2 H 2 )Ethyl 2-[4(1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

(2,2,2- 2 H 3 )Ethyl 2-[4-(1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

( 2 H 5 )Ethyl 2-[4-(1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

(1,1- 2 H 2 )Ethyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

(2,2,2- 2 H 3 )Ethyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate, and

( 2 H 5 )Ethyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate.

5. A pharmaceutically acceptable salt of a compound according to claim 1 which is selected from the group consisting of:

Ethyl 2-[4-(pyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-formylpyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-acetylpyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(trifluoroacetyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-[4-(1-propanoylpyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-propanoylpyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(cyclopropylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(cyclobutylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-{4-[1-(methoxycarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(methoxycarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(ethoxycarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-{4-[(2S)-1-(methylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(methylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(ethylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(dimethylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(1-methylpyrrolidin-2-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(N-methylglycyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[1-(methoxycarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(propan-2-ylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2,2,2-trifluoroethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(azetidin-1-ylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(morpholin-4-ylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(cyclopropylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(cyclobutylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2-methoxyethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(pyrrolidin-1-ylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(methoxycarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[methoxy(methyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(1-methylcyclobutyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(3-methyloxetan-3-yl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(3,3-difluoropyrrolidin-1-yl)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(3,3-difluorocyclobutyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(3,3-difluoroazetidin-1-yl)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-(4-{(2S)-1-[(2,2,2-trifluoroethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-(4-{(2S)-1-[(3,3-difluoroazetidin-1-yl)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[ethyl(propan-2-yl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(cyclobutyloxy)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2-fluoroethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2,2-difluoroethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(methoxyacetyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2-fluoroethoxy)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2,2,2-trifluoroethoxy)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(methylsulfanyl)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(2-methoxyethoxy)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-{[2-(dimethylamino)ethoxy]carbonyl}pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(hydroxyacetyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(3,3,3-trifluoropropanoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(pyridin-2-ylmethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[methyl(2,2,2-trifluoroethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(oxetan-3-ylcarbamoyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[methyl(oxetan-3-yl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-propanethioylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S,4S)-4-fluoro-1-propanoylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-4,4-difluoro-1-propanoylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-ethylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[3-(pyridin-2-yl)propanoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[methyl(pyridin-2-ylmethyl)carbamoyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[(pyridin-2-ylmethoxy)carbonyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-{N-[(benzyloxy)carbonyl]-□-alanyl}pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(□-alanyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-{[2-(methylamino)ethoxy]carbonyl}pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(2-fluoroethyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(2,2,2-trifluoroethyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(3,3,3-trifluoropropyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(2-methoxyethyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(2-methoxy-2-oxoethyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2S)-1-[2-(dimethylamino)-2-oxoethyl]pyrrolidin-2-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-benzylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(methylcarbamothioyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(methylcarbamoyl)-2,3-dihydro-1H-isoindol-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-phenylpyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Methyl 2-{4-[(2S)-1-(pyridin-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(pyridin-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(pyridin-4-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(pyrimidin-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(1,3-thiazol-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(1,3,4-thiadiazol-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-1-(5-methyl-1,3,4-oxadiazol-2-yl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate, and

Ethyl 2-{4-[(2S)-1-(5,7-dihydro-6H-pyrrolo [3,4-b]pyridin-6-ylcarbonyl)pyrrolidin-2-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate.

6. A pharmaceutically acceptable salt of a compound according to claim 1 which is selected from the group consisting of:

Ethyl 2-{4-[(2R)-2-(methoxycarbonyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-2-(methylcarbamoyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

1-{1-[6-(ethoxycarbonyl)-6-azaspiro[3.4]oct-2-yl]piperidin-4-yl}-4,4-difluoro-D-proline;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(methoxycarbonyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(methylcarbamoyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(dimethylcarbamoyl)-4,4-difluoropyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-carbamoyl-4,4-difluoropyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(methoxycarbamoyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-(4-{(2R)-4,4-difluoro-2-[methoxy(methyl)carbamoyl]pyrrolidin-1-yl}piperidin-1-yl)-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-4,4-difluoro-2-(methylcarbamoyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-2-(dimethylcarbamoyl)-4,4-difluoropyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(methoxycarbonyl)-2-methylpyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(6-oxo-7-oxa-1-azaspiro[4.4]non-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4S)-4-(methoxycarbonyl)-1,3-thiazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(3R)-3-fluoropyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(3S)-3-fluoropyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3,3-difluoropyrrolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-2-(trifluoromethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(fluoromethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(difluoromethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(trifluoromethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3-azabicyclo[3.1.0]hex-3-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-4,4-difluoro-2-methylpyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(methoxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(1-hydroxyethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-4,4-difluoro-2-(2-hydroxypropan-2-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2-oxopyrrolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2,5-dioxopyrrolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-methyl-5-oxopyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-ethyl-5-oxopyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-2-methyl-5-oxopyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2S)-2-ethyl-5-oxopyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2,2-dimethyl-5-oxopyrrolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4R)-4-methyl-2-oxo-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4R)-4-ethyl-2-oxo-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4R)-2-oxo-4-(propan-2-yl)-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4S)-4-methyl-2-oxo-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4S)-4-ethyl-2-oxo-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(4S)-2-oxo-4-(propan-2-yl)-1,3-oxazolidin-3-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(2-oxoimidazolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-[4-(3-methyl-2-oxoimidazolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(1H-pyrazol-5-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(1,2-oxazol-3-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(1H-tetrazol-5-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(2-methyl-2H-tetrazol-5-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[2-(1-methyl-1H-tetrazol-5-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(thiophen-2-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R)-2-(1,3-thiazol-2-yl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R,4R)-4-fluoro-2-(methoxycarbonyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R,4S)-4-fluoro-2-(methoxycarbonyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate;

Ethyl 2-{4-[(2R,4R)-4-fluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate, and

Ethyl 2-{4-[(2R,4S)-4-fluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate.

7. A compound according to claim 1 which is ethyl 2-[4-(1-methyl-1H-pyrazol-5-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

8. A compound according to claim 1 which is ethyl 2-{4-[(2R,4S)-4-fluoro-2-(methoxycarbonyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

9. A compound according to claim 1 which is ethyl 2-[4-(2-oxopyrrolidin-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

10. A compound according to claim 1 which is ethyl 2-{4-[(2R,4S)-4-fluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

11. A compound according to claim 1 which is ethyl 2-{4-[(2R)-4,4-difluoro-2-(1-hydroxyethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

12. A compound according to claim 1 which is ethyl 2-{4-[(2R,4R)-4-fluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

13. A compound according to claim 1 which is ethyl 2-{4-[(2R)-4,4-difluoro-2-(hydroxymethyl)pyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

14. A compound according to claim 1 which is ethyl 2-{4-[(2S)-2-ethyl-5-oxopyrrolidin-1-yl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

15. A compound according to claim 1 which is ethyl 2-[4-(1H-pyrazol-1-yl)piperidin-1-yl]-6-azaspiro[3.4]octane-6-carboxylate or a salt thereof.

16. A method of treating Alzheimer's Disease, dementia with Lewy bodies or schizophrenia, comprising administering to a subject in need thereof an effective amount of a compound according to claim 1 .