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

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

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

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

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

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

8-tert-butyl-4-(3-nitrobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-butyl-4-[2-(4-methoxyphenyl)acetyl]-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-butyl-4-(3,5-difluorobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

8-tert-butyl-4-(4-chloro-2-fluorobenzoyl)-1-oxa-4-azaspiro[4.5]decane-3-carboxylic acid

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