L-Seryl-L-leucine

The structure of L-seryl-L-leucine, C9H18N2O4, has been determined and anal ysed in relation to the geometries of its amino acid constituents. The most important feature is the different conformational behaviour of the side ch ains at the C-beta fi atoms; a less pronounced discrepancy concerns the ori entation of the C=O bond with respect to the C-alpha-N bond. The conformati onal preferences of these torsion angles are also established for related s tructures stored in the Cambridge Structural Database [Allen & Kennard (199 3). Chem. Des. Autom. News, 8, 1, 31-37]; the title structure compares well with these data. The molecules are organized in double layers, with the hy drophilic faces linked by an extensive hydrogen-bonding network, as in L-le ucine.