Synthesis of Hetero Atom Modified Pyrromethenones
A series of six heteroaromatic compounds, ethyl-/methyl- and dimethylfuranones, thiophenones, and cyclopentenones, was synthesized and condensed with a methyl methylpropionate substituted pyrrole, yielding the “right” half of open-chain tetrapyrroles. These compounds serve as light-inducible chromophores in the plant photoreceptor phytochrome. Three-dimensional structure analysis of the 10-oxapyrromethen-1-one 25 revealed a planar conformation, similar to the dipyrromethenone parent compound, stabilized by ahydrogen bond formed between the pyrrole proton and the furanone oxygen atom. All six pyrrole-substituted heteroaromatic derivatives 25–30 show absorbances in the visible spectrum with high molar extinction coefficients.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)