N2-(4-Methoxysalicylidene)arginine hemihydrate

The title compound, C14H20N4O4·0.5H2O [systematic name: (2S)-5-{[amino-(iminium-yl)meth-yl]amino}-2-{[(1Z)-4-meth-oxy-2-oxido-benzyl-idene]aza-nium-yl}penta-noate hemihydrate], has been synthesized by the reaction of l-arginine and 4-meth-oxy-salicyl-aldehyde and crystallizes with two independent substituted l-arginine mol-ecules and one water mol-ecule of solvation in the asymmetric unit. Each mol-ecule exists as a zwitterion and adopts a Z configuration about the central C=N. The mol-ecular conformation is stabilized by strong intra-molecular N-H⋯O hydrogen bonds that generate S(6) and S(10) ring motifs. Inter-molecular N-H⋯O and O-H⋯O hydrogen bonds involving also the water mol-ecule and weak inter-molecular C-H⋯Owater inter-actions link the mol-ecules into an infinite one-dimensional ribbon structure extending along the b axis. The known (2S) absolute configuration for l-arginine was invoked. Weak intermolecular C-H⋯π interactions are also present.