Molecular conformation of patellamide A, a cytotoxic cyclic peptide from the ascidian Lissoclinum patella, by X-ray crystal analysis.

As part of a series of investigations into the conformational stability of a C2-symmetric or related cyclic peptide isolated from the ascidian Lissoclinum patella, the molecular conformation of patellamide A, the chemical structure of which deviates slightly for C2-symmetry, was determined by X-ray crystal analysis. Patellamide A took on a saddle-shaped rectangular form and wrapped around the water and methanol solvents. This conformation which is very similar to that of C2-symmetric ascidiacyclamide would be proposed as a possible candidate for biologically "active" conformation.