CONFORMATION AND CRYSTAL STRUCTURE OF CYCLOTETRADEPSIPEPTIDE D-HYIV-L-MEILEU-D-HYIV-L-MELEU

The DLDL-cyclotetradepsipeptide ring consists of two α-hydroxy acid units in the trans conformation and two peptide units in the cis conformation. All the carbonyl groups extend in the same direction, roughly perpendicular to the average plane of the ring, while the hydrocarbon side chains extend in the opposite direction. All the side chains are in the fully extended form. The nitrogen atoms in the peptide groups are methyl substituted precluding any hydrogen bond formation. The material crystallizes in the orthorhombic space group P212121 with cell parameters α = 23.442 ± 0.006, b = 10.021 ± 0.003, and c = 11.524 ± 0.003 Å. The X-ray intensity data were collected with an automatic diffractometer. The crystal structure was solved by the symbolic addition procedure for phase determination as applied to noncentrosymmetric crystals. © 1969, American Chemical Society. All rights reserved.