Synthese von Betenamin und von Betalain-Modellsubstanzen |
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Authors: | Indu Parikh Hans Hilpert Kurt Hermann Andr S Dreiding |
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Institution: | Indu Parikh,Hans Hilpert,Kurt Hermann,Andrè S. Dreiding |
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Abstract: | Synthesis of Betenamine and of Betalaine Model Substances For comparisons of color, spectroscopic properties, pKa values, and stabilities, a number of model substances containing the 1,7-diazaheptamethinium chromophore 8 of the yellow and red betalaine plant pigments were prepared by the thermal or photolytic ring opening of simple pyridine derivatives (such as 2 and 14-16 ), followed by the introduction of amines. Among the novel compounds prepared were betenamine perchlorate ( 5 ), the ‘naked’ ring system of the beet-pigment betanine ( C ) as well as two 1,7-diazaheptamethinium salts 25 and 27 with terminal amono acids. The synthesis of 5 started with 4-(2-aminoethyl)pyridine ( 1 ) and proceeded via 2 , ring opening with indoline to 4 , saponification, and intramolecular amine replacement (Scheme 1). The syntheses of 25 and 27 involved only one step, namely ring opening of γ-picoline using (S)-cyclodopa ( 24 ) and (S)-proline ( 26 ), respectively (Scheme 3). |
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