In the title compound, C₁₃H₁₃N₅O₄·H₂O (4,5′-cyclo­wyosine·H₂O), the cyclization forces a syn arrangement of the aglycon with respect to the sugar moiety. The ribo­furan­ose part of the mol­ecule displays a β-D configuration with an envelope C1′-endo pucker. The mol­ecules are arranged in columns along the short a axis and are linked to water mol­ecules through O—HO and O—HN hydrogen bonds.