Glycyl-L-histidinium Chloride Dihydrate: an Unusual Histidine Conformation

The histidine side chain of the title compound, C₈H₁₃N₄O₃⁺.Cl⁻.2H₂O, is protonated and is incorporated in a tight N—H...X and C—H...X hydrogen-bonding pattern. The orientation of the imidazole moiety is unusual and associated with a short intramolecular C—H...O=C hydrogen bond from HisCδ—H to the peptide C=O. This configuration has not been observed previously with peptides.

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