Crystal and molecular structure of L‐lysyl‐L‐valine hydrochloride – a new lysine conformation

Thin plates of L‐lysyl‐L‐valine hydrochloride (C11H24N3O3Cl) were obtained using the vapour diffusion technique and analysed by X‐ray diffraction. The unit cell is orthorhombic, space group P212121, a = 5.465(6)Å, b = 19.657(4) Å, c = 13.522(2) Å, V = 1452.6(2.1) Å3 and Z = 4. The structure was solved by direct methods and refined to an agreement factor of 6.7% for 939 reflections with I > 3 σ(I). The lysine side chain conformation (g‐ g‐ tt) has never been found in peptide crystal structures, although it has been reported to occur in proteins. A network of hydrogen bonds between peptide molecules spreads along the a and c directions while no direct bonds are observed to occur between peptides along the b axis direction. This asymmetric pattern of interactions correlates with the crystal morphology.