Collect. Czech. Chem. Commun. 1989, 54, 160-165

The crystal and molecular structure of 4-phosphonomethyl-2-oxo-1-piperazinylacetic acid

František Pavelčík, Karol Havetta and Jaroslav Páterek

Department of Analytical Chemistry, Pharmaceutical School, J. A. Komenský University, 832 32 Bratislava


The structure of the title compound was determined by the method of X-ray diffraction of single crystals. The substance crystallizes in the P21/c monoclinic space group. The structure was refined by the least squares method to R = 0.044 on the basis of 2 076 observed reflections. It was found that this compound is not a dicarboxylic acid but rather an intramolecularly cyclized lactam. The hydrogen phosphonato functional group participates in the betain form, while the carboxyl group is not ionized. The conformation of the six-membered oxopiperazine ring is similar to that of cyclohexane in which the peptidic group plays a similar role to the double bond.