A β-sheet structure formed by C-H•••O hydrogen bonds between the thiazole rings and amide bonds of a dimeric desoxazoline ascidiacyclamide analogue

A dimeric analogue of desoxazoline ascidiacyclamide was synthesized to increase the conformational flexibility of the molecule. The overall structure of this compound, C72H112N16O16S4. 3C(3)H(7)NO .H2O, was relatively flat and was classified neither as the folded nor squared form, which have been observed in ascidiacyclamide analogues. Rather, a unique beta -sheet was formed in the 48-membered ring with pseudo-twofold symmetry. This was stabilized by hydrogen bonds including C-H . . .O interactions between thiazole and carbonyl O atoms. This is the first structure of an ascidiacyclamide analogue to exhibit a flat conformation composed of a eta -sheet.