Patellamide A, a cytotoxic cyclic peptide from the ascidian Lissoclinum patella

The structure of crystals of patellamide A (13-methyl-9,23-bis(1-methylethyl)-2,16-bis(1-methylpropyl)-14,-28-di oxa-7,21- dithia-3,10,17,24,29,30,31,32- octaaza-pentacyclo[24.2.1.1(5,8).1(12,15).1(19,22]dotriac onta-1(29),5,- 8(30),15(31),19,22(32)-hexaene-4,11,18,25-tetraone methanol solvate monohydrate, C35H49N8O6S2.-CH4O.H2O), a cytotoxic cyclic peptide having a non-C2-symmetric methyl group, shows the C2-symmetric and saddle-shaped rectangular conformation where the methyl group is disordered into two C2-symmetric positions. The water and methanol solvents were located on the crystallographic diad axis and were held by hydrogen bonds and van der Waals contacts with the polar ring N atoms and non-polar D-Val side-chain atoms, respectively.