N (2)-(4-Meth­oxy­salicyl­idene)arginine hemihydrate

The title compound, C(14)H(20)N(4)O(4)·0.5H(2)O [systematic name: (2S)-5-{[amino­(iminium­yl)meth­yl]amino}-2-{[(1Z)-4-meth­oxy-2-oxido­benzyl­idene]aza­nium­yl}penta­noate hemihydrate], has been synthesized by the reaction of l-arginine and 4-meth­oxy­salicyl­aldehyde and crystallizes with two independent substituted l-arginine mol­ecules and one water mol­ecule of solvation in the asymmetric unit. Each mol­ecule exists as a zwitterion and adopts a Z configuration about the central C=N. The mol­ecular conformation is stabilized by strong intra­molecular N—H⋯O hydrogen bonds that generate S(6) and S(10) ring motifs. Inter­molecular N—H⋯O and O—H⋯O hydrogen bonds involving also the water mol­ecule and weak inter­molecular C—H⋯O(water) inter­actions link the mol­ecules 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.