X-ray crystal structure of the hexadepsipeptide cycle (Gly-Lac-Lac)(2) with lactyl beta-turns

Two crystal forms of the depsipeptide cycle (Gly-Lac-Lac)(2) have been char acterized. One of them only gives small crystals; from the other form we ha ve determined the structure by single crystal X-ray diffraction. The genera l cyclic shape of the molecule is a ring with two beta-turns, each of which involves two lactyl residues. The two beta-turns are different and have ra ther extreme conformational angles, when compared with proteins. Neverthele ss this type of rings may be useful as analogs of some regions of proteins, while novel conformational features are found, due to the presence of hydr ogen bonds between amino hydrogens and the eater oxygen.