Beiträge zur Chemie der Pyrrolpigmente, XXXIII [1] Darstellung, Struktur und Eigenschaften von isomeren N-Methyl-Bilatrienen-abc (N-Methyl-etiobiliverdine-IV-γ) / On the Chemistry of Pyrrole Pigments, XXXIII [1] Synthesis, Structure and Properties of Isomeric N-Methyl-bilatrienes-abc (N-Methyl-etiobiliverdines-IV-γ)

Abstract

Methylation of etiobiliverdin-IV-γ yields a ring-A N-methylated product the structure of which was proven by comparison with the corresponding monolactimether and the ring-B methylated product which was synthesized on an independent route. The configura-tion (Z,Z,Z) was deduced by ¹H-NMR experiments and a more or less helical conformation which is most twisted at the ring-A methine fragment was found. Photoisomerization exclusively takes place at this position giving the (E,Z,Z) diastereomer, a reaction which is discussed in terms of the correlation of light absorption, methine single bond twist and photochemical selectivity.