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

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

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

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

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

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

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