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

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

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

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

4-(4-methyl-3-nitrobenzoyl)-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

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

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

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

8-benzyl-4-(4-fluorobenzoyl)-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