Zur Chemie der Pyrrolpigmente, 63. Mitt. |
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Authors: | Heinz Falk Norbert Müller Silvia Wansch |
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Institution: | (1) Institut für Analytische, Organische und Physikalische Chemie, Johannes-Kepler-Universität, A-4040 Linz, Österreich |
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Abstract: | Using hexamethylphosphoric acid triamide (HMPT) as solvent for bilatrienesabc and mainly for 2,3-dihydrobilatrienes-abc (which serve as the most suitable models for the biliproteid chromophores) a small hypsochromic shift and a dramatic change of the relative intensities of short and long wavelength absorption bands, as compared to solutions in CCl4, is observed. Applying NMR-spectroscopic techniques (15N-,13C-,1H-) a predominance of the (4Z,9E,15Z) diastereomer forming a 5syn-, 10anti-, 14syn-periplanar orclinal conformation is deduced. The stabilisation of this configuration and conformation arises from strong hydrogen bonds between the acidic protons of the bilins andHMPT. Interactions of this kind seem to be the main source of energy to stretch the otherwise coiled bilin chromophore of (4Z,9Z,15Z)-5sp,10sp,14sp geometry. Stretched systems of the type bilin-HMPT may serve as a valuable model for the natural biliproteides.Herrn Prof. Dr.A. Eschenmoser zum 60. Geburtstag gewidmet.116, 1065 (1985). |
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Keywords: | Phytochrome models 2 3-Dihydrobilatrienes-abc Hexamethylphosphoric acid triamide Stretched chromophore-conformation NMR-techniques |
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