4-(2,5-Difluorobenzoyl)-8-ethyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

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

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

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

4-(2,5-difluorobenzoyl)-8-propyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

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

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

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

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

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

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

4-acetyl-8-benzyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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