Synthesis of oligomethylene-strapped chlorophyll derivatives and optical properties of their stereoisomers in a solution

Photosynth Res. 2012 Mar;111(1-2):1-8. doi: 10.1007/s11120-010-9616-y. Epub 2011 Jan 21.

Abstract

Methyl pheophorbide-a/a' derivatives covalently linked with oligomethylene chains at the 3-CH(2)OCO- and 13(2)-COO- moieties in a molecule were prepared by modifying chlorophyll-a through intramolecular ring-closing metathesis of vinyl groups. At least, a C10-length between the 3(3)- and 13(4)-positions was necessary for the cyclization and connection of a C12-strap was the most suitable to achieve the highest closure yield. The oligomethylene chain in 13(2) R-epimers derived from methyl pheophorbide-a covered the α-face of the chlorin π-plane and the strap in the corresponding 13(2) S-epimers protected the β-face. Synthetic 13(2) R-epimer with a dodecamethylene chain gave a flat chlorin π-plane, while the decamethylene chain in the 13(2) R-epimer distorted the π-system due to its shorter linkage. The distortion by strapping in the 13(2) R-epimer induced a slight blue-shift of Qy peak in dichloromethane. CD spectra of the 13(2) R-epimers were similarly dependent on the chain length, i.e., the distortion of π-plane. Visible absorption and CD spectra of all the strapped 13(2) S-epimers were almost identical and only slightly different from those of the unstrapped. The strapping in the 13(2) S-epimers shifted the Qy peak bathochromically.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chlorophyll / analogs & derivatives*
  • Chlorophyll / chemical synthesis
  • Chlorophyll / chemistry
  • Chlorophyll A
  • Circular Dichroism
  • Models, Molecular
  • Molecular Conformation
  • Optics and Photonics
  • Solutions
  • Spectrophotometry, Atomic
  • Spirulina / chemistry*
  • Stereoisomerism

Substances

  • Solutions
  • Chlorophyll
  • methylpheophorbide
  • pheophorbide a
  • Chlorophyll A