Diisopropyl 3,3-dimethoxycyclobutane-1,1-dicarboxylate;3,3-di(isopropoxycarbonyl)-1,1-dimethoxycyclobutane;3,3-dimethoxy-cyclobutane-1,1-dicarboxylic acid diisopropyl ester;bis(1-methylethyl) 3,3-dimethoxycyclobutane-1,1-dicarboxylate;