4-(3,5-dinitrobenzoyl)-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

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

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

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

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

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

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

8-ethyl-4-(2,4,6-trimethylbenzoyl)-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

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