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

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

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

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

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

8-benzyl-4-pentanoyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

8-benzyl-4-cyclopropanecarbonyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid

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

8-benzyl-4-heptanoyl-1-oxa-4,8-diazaspiro[4.5]decane-3-carboxylic acid