amide of cis-3-azidocyclobutane-1-carboxylic acid
methylester of 3-p-toluenesulfonyloxycyclobutane-1-carboxylic acid
amide of 3-p-toluenesulfonyloxycyclobutane-1-carboxylic acid
3-(benzyloxy)cyclobutane-1,1-dicarboxylic acid
methylester of 3-benzyloxycyclobutane-1-carboxylic acid