Synthesis and the Solid-State Conformations of Cross-Linked Resin-Bound Oligo(leucine)s.1,2 Internal Aggregations through the Intermolecular Hydrogen Bonding of the Oligopeptides on the Polymer Networks

Abstract

Cross-linked and soluble polystyrene resin-bound oligo(leucine)s were prepared by the step-by-step coupling of Boc-Leu3-OH to H-Phe-resins using dicyclohexylcarbodiimide and 1-hydroxy-1H-benzotriazole. The solid state conformational analysis of H–(–Leu3–)–nPhe-resins (n=1—5), cross-linked resin; n=1—3, soluble resin) by infrared spectroscopy indicated that the pep-tide chains had various conformations depending on the chain length: n=1, essentially an unordered conformation; n=2—4, mainly the β-structure; and n=5, predominantly the α-helix. The formation of the β-structure indicates that resin-bound peptide chains can easily interact with each other through hydrogen bonds even in polymer networks. The correlation of the conformation in the swollen state with that in the solid state was examined using various solvents. Effects of shear stress on conformational transformations of H–(–Leu3–)–nPhe-resins (n=1—3) was also examined.