Structure of Hormaomycin, a Naturally Occurring Cyclic Octadepsipeptide, in the Crystal

The structure of hormaomycin has been determined in two crystals grown under different conditions, i. e. in the absence and in the presence of magnesium chloride. In both crystals, the macrocyclic hexadepsipeptide assumes a rather flat conformation, and the dipeptide side chain resides in the same equatorial plane. This is a significant difference in comparison with the compact bent conformation of hormaomycin in solution, as previously determined by an extensive NMR study