Structure and atropisomerisation of new diastereomeric gossypol Schiff bases with (R)-(+)-2-amino-3-benzyloxy-1-propanol studied by NMR, ECD and DFT methods

Przybylski, Piotr; Kwit, Marcin; Pyta, Krystian; Pankiewicz, Radosław; Schroeder, Grzegorz; Gawroński, Jacek; Brzeziński, Bogumił

doi:10.1016/j.tetasy.2010.05.034

Cited by 6 publications

(8 citation statements)

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“…The double hybrid approach substitutes part of the correlation functional by a perturbative contribution obtained with a MP2 or CIS(D) treatment. These models have shown a more accurate evaluation of the excitation energies, but at the present time, only a few AC assignments have been presented 180,181…”

Section: Application Of Conformational Analysis To the Determination mentioning

confidence: 99%

Recent trends in conformational analysis

Mazzanti

Casarini

2011

WIREs Comput Mol Sci

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An outlook of the various research fields of organic chemistry where conformational analysis plays a fundamental role is presented. The section Methodologies for Conformational Analysis is focused on the information that can be obtained by various spectroscopic techniques such as nuclear magnetic resonance and optical methods such as electronic circular dichroism and vibrational circular dichroism. A comprehensive screening of the more recent ab initio and density functional theory theoretical approaches to conformational analysis is presented in the section Theoretical Conformational Analysis. The section Application of Conformational Analysis to the Determination of the AC of Organic Molecules shows how the synergic use of experimental and theoretical methods can solve challenging conformational tasks arising from modern organic chemistry. © 2011 John Wiley & Sons, Ltd. This article is categorized under: Electronic Structure Theory > Density Functional Theory

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Section: Application Of Conformational Analysis To the Determination mentioning

confidence: 99%

Recent trends in conformational analysis

Mazzanti

Casarini

2011

WIREs Comput Mol Sci

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“…For this reason, studies were carried out to transform gossypol into diastereoisomeric Schiff bases to separate the racemic mixture. However, it was very difficult to obtain the enantiomers of gossypol [24,25]. Further studies on gossypol Schiff base indicated that the compound existed in solution as two tautomeric forms of enamine–enamine and imine–imine [26] However, it was difficult to evaluate the stability of gossypol without systematical and sufficient data.…”

Section: Introductionmentioning

confidence: 99%

Investigating Stability and Tautomerization of Gossypol—A Spectroscopy Study

et al. 2019

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The stability of gossypol was investigated by the spectroscopic method. Gossypol was dissolved in three different solvents (CHCl3, DMSO, and CH3OH) under different storage conditions (dark and with nitrogen protection, natural light and with nitrogen protection, ambient air conditions) for different time intervals (0 days, 3 days, 5 days, 7 days, 15 days, 30 days, and 45 days) at room temperature. Then, the stability of gossypol was investigated by 1H NMR, UV-vis, and HPLC-QTOF-MS spectrometry. Results showed that gossypol existed in aldehyde–aldehyde form in chloroform within five days. Then, both aldehyde–aldehyde and lactol–lactol tautomeric forms existed and maintained a stable solution for 45 days. Gossypol dissolved in methanol mainly existed in aldehyde–aldehyde form. Only a tiny amount of lactol–lactol was found in freshly prepared methanol solution. Gossypol was found to only exist in lactol–lactol form between 30–45 days. Gossypol existed in aldehyde–aldehyde, lactol–lactol, and ketol–ketol forms in dimethyl sulfoxide, and there was a competitive relationship between aldehyde–aldehyde and lactol–lactol form during the 45 days. Among all the solvents and conditions studied, gossypol was found to be highly stable in chloroform. Under the tested conditions, the natural light and atmospheric oxygen had little effect on its stability. Although the spectroscopy data seemed to be changed over time in the three different solvents, it was actually due to the tautomeric transformation rather than molecular decomposition.

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“…37 The ratio of the diastereomers was established on the basis of the integrals of selected 1 H signals (H-1 and H-11). The atropisomerisation of the gossypol Schiff base took place even if the samples were not exposed to the sunlight, however, this process was slower in the dark.…”

Section: Racemisation or Epimerisation Of Iminesmentioning

confidence: 99%

“…Methyltrioxorhenium(VII) (MTO) forms mono-or bis-complexes with di-Schiff bases being derivatives of various salicylaldehydes and trans-1,2-diaminocyclohexane [37]. 90 [37] The small differences in chemical shifts of coordinated and uncoordinated MTO signals in 1 H NMR spectra indicate a weak MTO-Schiff base interaction in solution at room temperature.…”

Section: Re(vii) Complexesmentioning

confidence: 99%