A water wire in L‐prolyl‐L‐serine monohydrate

Despite the extra functional group in the serine side chain, the crystal packing arrangement of the title compound {systematic name: (S)‐3‐hydroxy‐2‐(S)‐pyrrolidine‐2‐carboxamido]propanoic acid monohydrate}, C₈H₁₄N₂O₄·H₂O, is essentially the same as observed for a series of L‐Pro‐L‐Nop peptide hydrates, where Nop is a strictly nonpolar residue. This is rendered possible by a monoclinic P2₁ packing arrangement with Z′ = 2 that deviates from orthorhombic P2₁2₁2₁ symmetry only for the seryl hydroxy groups, which form infinite O—H...O—H hydrogen‐bonded chains along the 5.3 Åa axis. At the same time, cocrystallized water molecules form parallel water wires.