8-methyl-4-[2-(trifluoromethyl)benzoyl]-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

4-[2-(4-methoxyphenyl)acetyl]-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(2-bromobenzoyl)-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(2,4-difluorobenzoyl)-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(4-chloro-2-fluorobenzoyl)-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

8-ethyl-4-(3-phenylpropanoyl)-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(4-tert-butylbenzoyl)-8-ethyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

8-ethyl-4-[4-(trifluoromethyl)benzoyl]-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-[4-(dimethylamino)benzoyl]-8-ethyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(2-ethoxybenzoyl)-8-ethyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

4-(3-phenylpropanoyl)-8-propyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid