title: (R)-Methyl {[(2-carb-oxy-bicyclo-[2.2.2]octan-1-yl)-ammonio]-methyl}-phos-phon-ate dichloro-methane 0.25-solvate.
abstract: The carb-oxy-lic acid mol-ecule of the title compound, C(11)H(20)NO(5)P·0.25CH(2)Cl(2), exists as a zwitterion with the H atom of the phospho-nate group being transferred to the imine N atom. In the asymmetric unit, there are two crystallographically independent acid mol-ecules adopting the same absolute configuration and differing slightly in their geometrical parameters. In each mol-ecule, the imino and carboxyl groups are connected via an intra-molecular N-H⋯O hydrogen bond. Inter-molecular O-H⋯O and N-H⋯O hydrogen bonds induce the formation of layers parallel to the ab plane. The dichloro-methane solvent mol-ecule, with a site occupancy of 0.5, is located between the layers.
authors.forename: Petar
authors.initials: P
authors.lastname: Todorov
authors.forename: Monique
authors.initials: M
authors.lastname: Calmes
authors.forename: Boris L
authors.initials: BL
authors.lastname: Shivachev
authors.forename: Rosica P
authors.initials: RP
authors.lastname: Nikolova
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