Methanol-mediated, modular self-assembly of antiparallel beta-dimers. Crystal structure of C alpha backbone-modified tripeptide Bz-Aib-NHCOCO-Aib-OMe.

Abstract

The backbone-modified tripeptide Bz-Aib-NHCOCO-Aib-OMe, in which the central C alpha has been replaced with CO, self-assembles in the solid state into highly ordered two-dimensional arrays through MeOH mediated intermolecular stacking of dimeric 'disk' modules formed by an antiparallel beta-sheet-type arrangement of tripeptide molecules. The C alpha(C'O)N(C'O)(C')NC alpha segment is nearly coplanar (average deviation from a mean least-square plane is +/- 0.037 A). The oxalyl moiety forms two pseudo-C5 intramolecular hydrogen bonds. Crystal parameters are as follows: C18H23N3)6.CH3OH, triclinic space group P1-, alpha = 9.796(4), b = 10.348(3), c = 11.836(4) A, alpha = 78.28(3), beta = 73.72(3), gamma = 69.45(3), R = 0.082 for 1747 reflections measured with [formula: see text].