CORE DIRECTED SELF-ASSEMBLIES IN THE SOLID-STATE OF RETRO AIB BIS-PEPTIDE DICARBOXYLIC-ACIDS - A DESIGN STRATEGY FOR CONTROL OF MOLECULAR-ORIENTATION IN PEPTIDES

Self-assembly patterns as a function of the central core insert in the retro bis-peptide dicarboxylic acids HO-Aib-X-Aib-OH, containing oxalyl (-CO-CO-; 1), fumaryl (-CO-CH=CH-CO-;2), and adipoyl [-CO-(CH2)(4)-CO-;3], have been characterized by single crystal x-ray diffraction analyses. Extensive hydrogen bonding occurs in each crystal but there are no OH...O bonds between acid groups. Only two types of hydrogen bonds occur in all the crystals: NH...O (acid terminal), 2.84-2.98 Angstrom and OH (acid terminal)...O (core carbonyl), 2.55-2.67 Angstrom (except for an additional intramolecular C-5 type bond in the oxalyl moiety in 1). The self-assembly patterns are a beta-network in 1, separate layer assemblies (beta-networks) for two independent molecules in 2 that combine into a three-dimensional gamma network, and separate ribbon assembles (alpha networks) for two independent molecules in 3 that combine into an extended beta-network sheet with hydrophobic faces. (C) 1995 John Wiley and Sons, Inc.