Synthesis of diacetylene-containing peptide building blocks and amphiphiles, their self-assembly and topochemical polymerization in organic solvents

Chemistry. 2009;15(2):388-404. doi: 10.1002/chem.200801668.

Abstract

A series of functional iodoacetylenes was prepared and converted into the corresponding diacetylene-substituted amino acids and peptides via Pd/Cu-promoted sp-sp carbon cross-coupling reactions. The unsymmetrically substituted diacetylenes can be incorporated into oligopeptides without a change in the oligopeptide strand's directionality. Thus, a series of oligopeptide-based, amphiphilic diacetylene model compounds was synthesized, and their self-organization as well as their UV-induced topochemical polymerizability was investigated in comparison to related polymer-substituted macromonomers. Solution-phase IR spectroscopy, gelation experiments, and UV spectroscopy helped to confirm that a minimum of five N-H...O=C hydrogen-bonding sites was required in order to obtain reliable aggregation into stable beta-sheet-type secondary structures in organic solvents. Furthermore, the non-equidistant spacing of these hydrogen-bonding sites was proven to invariably lead to beta-sheets with a parallel beta-strand orientation, and the characteristic IR-spectroscopic signatures of the latter in organic solution was identified. Scanning force micrographs of the organogels revealed that compounds with six hydrogen-bonding sites gave rise to high aspect ratio nanoscopic fibrils with helical superstructures but, in contrast to the related macromonomers, did not lead to uniform supramolecular polymers. The UV-induced topochemical polymerization within the beta-sheet aggregates was successful, proving parallel beta-strand orientation and highlighting the effect of the number and pattern of N-H...O=C hydrogen-bonding sites as well as the hydrophobic residue in the molecular structure on the formation of higher structures and reactivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylene / chemistry*
  • Circular Dichroism
  • Hydrogen Bonding
  • Hydrophobic and Hydrophilic Interactions
  • Microscopy, Atomic Force
  • Molecular Weight
  • Oligopeptides / chemical synthesis*
  • Oligopeptides / chemistry
  • Pargyline / analogs & derivatives
  • Pargyline / chemistry
  • Polymers / chemistry*
  • Propylamines / chemistry
  • Solvents / chemistry*
  • Spectrophotometry, Infrared
  • Spectrophotometry, Ultraviolet
  • Surface-Active Agents / chemical synthesis*
  • Surface-Active Agents / chemistry

Substances

  • Oligopeptides
  • Polymers
  • Propylamines
  • Solvents
  • Surface-Active Agents
  • propargylamine
  • Pargyline
  • Acetylene