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

8-tert-butyl-4-(4-fluorobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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

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

8-tert-butyl-4-(2-methylbenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-butyl-4-(3-fluorobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-Butyl-4-(2,4-difluorobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-butyl-4-[4-(dimethylamino)benzoyl]-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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

8-benzyl-4-(furan-2-carbonyl)-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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