4-(4-tert-butylbenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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

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

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

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

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

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

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

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