4-(4-chloro-3-nitrobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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

4-{[1,1'-biphenyl]-4-carbonyl}-8-methyl-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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

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

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

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

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

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

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

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