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

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

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

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

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

8-ethyl-4-(naphthalene-1-carbonyl)-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