Hydrogen Bonded Squaramide-Based Foldable Module Induces Both beta- and alpha-Turns in Hairpin Structures of alpha-Peptides in Water

摘要

A novel tertiary squaramido-based reverse-turn module SQ is reported, and its conformational properties are evaluated. This module is easily incorporated into a alpha-peptide sequence by conventional solid-phase peptide synthesis. The structure characterization of the hybrid squaramido-peptide 4 is described, showing that the turn segment induces the formation of hairpin structures in water through the formation of both alpha SQ- and beta SQ-turns.