Synthesis, reactivity and conformational preferences of novel enediynyl peptides: a possible scaffold for β-sheet capping turns

摘要

Novel enediynyl tripeptides 2(a–c) in fully protected forms have been prepared via a sequence of palladium()-basednSonogashira coupling. The thermal reactivity of these peptides was shown to be dependent upon the nature of thenside chain in the amino acids. Analysis of the CD-spectra of these peptides as well as the variation of chemical shiftsnwith temperature revealed the presence of a β-sheet nucleating conformation in equilibrium with a conformationninduced by H-bond formation between the CO and NH belonging to the enediynyl amino acid.