2010
DOI: 10.1039/c0ob00288g
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The influence of protonation on molecular structure and physico-chemical properties of gossypol Schiff bases

Abstract: Protonation of gossypol Schiff bases (S1 and S2), possessing different numbers of basic N-atoms, was studied using potentiometric, spectroscopic, ESI MS and PM5 methods. Titration of S1 and S2 with HClO(4), monitored by the FT-IR and (1)H NMR, indicated that the change from the enamine-enamine into the protonated imine-imine tautomeric form occurs at different Schiff base-H(+) ratio. The FT-IR and PM5 results show that for S1 the first protonation step occurs at Schiff base moiety whereas for S2 it is realised… Show more

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Cited by 12 publications
(8 citation statements)
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“…Protonation has long been recognized as a fundamental process that plays an important role in many chemical and biological reactions. [1][2][3][4][5] For molecules with multiple functional groups, protonation may take place at different sites, resulting in different forms of protonated molecules. The thermodynamically favored site of protonation is mainly dependent on the proton affinity (PA) 6 at each local functionality of the molecule.…”
Section: Introductionmentioning
confidence: 99%
“…Protonation has long been recognized as a fundamental process that plays an important role in many chemical and biological reactions. [1][2][3][4][5] For molecules with multiple functional groups, protonation may take place at different sites, resulting in different forms of protonated molecules. The thermodynamically favored site of protonation is mainly dependent on the proton affinity (PA) 6 at each local functionality of the molecule.…”
Section: Introductionmentioning
confidence: 99%
“…Furthermore its structure was confirmed by HSQC ( 1 H‐ 13 C heteronuclear single quantum coherence spectroscopy, Figure S7, Supporting Information). As mentioned above, the unusual stability of such Schiff's bases resulting from nucleophilic addition of Gossypol with amines has been described before and can be attributed to stabilization through intramolecular hydrogen bonds as indicated in Figure . The question remained, whether it was the thiazolidine conjugate 1 a or its imine congener 1 b , which was responsible for the encouraging selective cell toxicity observed in the initial experiments.…”
Section: Figurementioning
confidence: 69%
“…An imine‐based linkage through an Ala‐modified homing peptide was also explored ( 1 b ). Gossypol is known to form comparably stable conjugates with amines as well as small peptides, as the resulting Schiff's base is stabilized by two cooperative intramolecular hydrogen bonds formed by the ortho ‐ and meta ‐hydroxyl groups …”
Section: Figurementioning
confidence: 99%
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