Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5272410 | Tetrahedron Letters | 2013 | 5 Pages |
Abstract
The equilibrium forms of carboxypyranomalvidin-3-O-glucoside (vitisin A) were studied in aqueous solution at different pH values by NMR and UV-Visible spectroscopy. The results obtained revealed the presence of three deprotonation reactions at positions 10-COOH, 7-OH and 4â²-OH: pKa1 = 1.09 ± 0.09; pKa2 = 4.93 ± 0.02; pKa3 = 9.14 ± 0.05, data obtained from NMR titration. The titration by NMR confirmed the absence of hydration reactions since no characteristic peaks of the hemiketal form were observed in the NMR spectrum at any pD value studied (pD 0.67-10.99).
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Physical Sciences and Engineering
Chemistry
Organic Chemistry
Authors
Joana Oliveira, Nuno Mateus, Victor de Freitas,