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

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

4-benzoyl-8-methyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

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

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

4-{[1,1'-biphenyl]-4-carbonyl}-8-ethyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

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