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10. Conjugation Length Dependence of Free Radical Scavenging Efficiency of Retinal and Retinylisoflavonoid Homologues

Author

Jiang, Yang-Lin, Chen, Bai-Ling, Yan, Xiao-Kun, Xu, Yi, Zhao, Chen-Chen, Chen, Zi-Li, Wang, Peng, Zhang, Jian-Ping, Skibsted, Leif H., Jiang, Yang-Lin, Chen, Bai-Ling, Yan, Xiao-Kun, Xu, Yi, Zhao, Chen-Chen, Chen, Zi-Li, Wang, Peng, Zhang, Jian-Ping, and Skibsted, Leif H.

Abstract

Retinal (C20) and the C25 and C30 homologues were compared as radical scavengers together with their C22, C27, and C32 homologues linked with daidzein through a B′3 (isoflavonoid) to oxo-carbon (aldehyde) covalent bond. Oxidation potential in acetonitrile determined by cyclic voltammetry and ionization potential calculated by density functional theory for the aldehydes and dyads (conjugates), of which the two longer are new, decreased linearly with the wavenumber for absorption maximum. The logarithm of the second-order rate constant for scavenging of the ABTS•+ increased linearly with decreasing oxidation potential suggesting that longer conjugation in the antioxidant increases the rate of electron transfer. A similar linear free energy relationship was found for the rate of scavenging DPPH•, including daidzein, which may indicate involvement of hydrogen atom transfer from an isoflavonoid phenol. Prediction of radical scavenging efficiency from visible absorption spectra was demonstrated with the perspective of rational design of bifunctional amphiphilic antioxidants.

Published
2020

15. Highly diastereoselective addition of alkynylmagnesium chlorides to N-tert-butanesulfinyl aldimines: a practical and general access to chiral alpha-branched amines.

Author

Chen BL, Wang B, and Lin GQ

Subjects
Imines chemistry, Magnetic Resonance Spectroscopy, Molecular Structure, Stereoisomerism, Sulfhydryl Compounds chemistry, Alkynes chemistry, Amines chemistry, Imines chemical synthesis, Magnesium Chloride chemistry, Sulfhydryl Compounds chemical synthesis
Abstract

The addition of alkynylmagnesium chlorides to N-tert-butanesulfinyl imines proceeded with a remarkably high diastereoselectivity (dr > 13:1, mostly diastereopure), and with a general scope of both reaction partners. The high dr translated into simplified purification and higher optical purity for the synthesis of a wide array of chiral alpha-branched amines. The alkyne functionality also provides a multitude of opportunities for further synthetic transformations. The short asymmetric synthesis of (+)-angustureine 7 and (-)-cuspareine 10 was realized with use of this approach.

Published
2010
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