Zur photochemischen (Z)⇆(E)-Isomerisierung von Gallenpigment-Partialstrukturen

摘要

The photochemical (Z)⇆(E) isomerization of the exocyclic double bond is only possible in pyrromethenones (partial structure1) but not in2–4. From spectral investigations, chelation and methylation of certain positions within these structures it can be shown that it is most probably a proton transfer reaction which competes successfully with the isomerizat