On the Chemistry of Pyrrole Pigments. XXXV: A Reversible Regioselective Addition to Bilatrienes-abc

Article abstract of DOI:10.1007/BF00938725

Using spectroscopic methods (UV-VIS, 1H-NMR) the reversible addition of donors (alcohols, amines, thiols, HCN, bisulfit and C-H acidic compounds) to bilatrienes-abc was investigated.This equilibrium is in close analogy to the addition of donors to a carbonyl group (as was deduced from thermodynamic and kinetic measurements) and is also the basis for understanding the photochemical isomerization of bilatrienes-abc in the adsorbed state.Based thereon a recipe for the isomerization of bilatrienes-abc in homogeneous phase giving high yields of the (E,Z,Z)-diastereomer is presented: in addition the (E,Z,E)-diastereomer of aetiobiliverdin-IV-γ was isolated and characterized for the first time.A model compound representing the intramolecular addition of a donor attached to a side chain (mimicking a peptide unit) was synthesized and studied with respect to its photochemical behaviour. - Keywords: Bilatrienes-abc; Photoisomerization; Reversible Addition