Format of Original
International Union of Crystallography
Acta Crystallographica Section E: Crystallographic Communications
Original Item ID
The title compound, C6H9NO4·H2O [systematic name: (αR,1R,2S)-rel-α-amino-2-carboxycyclopropaneacetic acid monohydrate], crystallizes with two organic molecules and two water molecules in the asymmetric unit. The space group is P21 and the organic molecules are enantiomers, thus this is an example of a `false conglomerate' with two molecules of opposite handedness in the asymmetric unit (r.m.s. overlay fit = 0.056 Å for one molecule and its inverted partner). Each molecule exists as a zwitterion, with proton transfer from the amino acid carboxylic acid group to the amine group. In the crystal, the components are linked by N-H···O and O-H···O hydrogen bonds, generating (100) sheets. Conformationally restricted glutamate analogs are of interest due to their selective activation of different glutamate receptors, and the naturally occurring (+)-CCG-III is an inhibitor of glutamate uptake and the key geometrical parameters are discussed.