5,7-Dichlorokynurenic Acid Hydrate, an Antagonist for the Glycine Binding Site on the NMDA Receptor

The structure of 5,7-dichlorokynurenic acid hydrate (IUPAC name: 5,7-dichloro-4-oxo-1,4-dihydro-2-quinolinecarboxylic acid hydrate), C₁₀H₅Cl₂NO₃.H₂O, has been determined by X-ray analysis. The molecule exists as a keto tautomer. All hydrogen-bond donors and acceptors take part in the hydrogen-bonding network which connects molecules into a three-dimensional array. Graph set analysis shows that there are both rings and chains in the network; however, there are no carboxylic acid dimers. The O-H portion of the carboxylic acid group is in a trans orientation with respect to the N-H group of the bicyclic ring system; the plane of the carboxylic group makes an angle of 7.6 (2)° with the plane of heterocyclic ring.

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