Molecular aggregation in selected crystalline 1 : 1 complexes of hydrophohic D- and L-amino acids. III. The L-leucine and L-valine series

The amino acids L-leucine (L-Leu) and L-valine (L-Val) have been cocrystallized with D-aminobutanoic acid (D-Abu), D-2aminopentanoic acid (D-Nva) and D-methionine (D-Met) to form six complexes, L-Leu:D-Abu, C6H13NO2. C4H9NO2, L-Leu:D-Nva, C6H13NO2. C5H11NO2, L-Leu:D-Met, C6H13NO2. C5H11NO2S, L-Val:D-Abu, C5H11NO2. C4H9NO2, L-Val:D-Nva, C5H11NO2. C5H11NO2 and L-Val:D-Met, C5H11NO2. C5H11NO2S. A fourth L-Leu complex, with D-Val, C6H13NO2. C5H11NO2 has also been studied. The crystals of these amino acid complexes are all divided into distinct hydrophilic and hydrophobic layers. The D- and L-amino acids are all related by pseudo-inversion in the L-Leu complexes and by pseudo-glide planes in the L-Val series. Similarities and differences in the crystal packing and molecular conformations of L-Leu/L-Val, as well as of the partner molecules, are discussed.