Reactivity of Selenocystine and Tellurocystine: Structure and Antioxidant Activity of the Derivatives

Abstract

l-Selenocystine (5) and l-tellurocystine (6) have been prepared and the reactivity of these amino acids, i.e., oxidation of 5 and 6, has been performed at various pH values. Hydrogen peroxide was used as an oxidant and it was treated with 5 and 6 in excess in acidic and basic media. Compound 5, upon oxidation, afforded Se and Se products. Selenocysteic acid [HO SeCH CH(NH )COOH] 9, a novel Se compound, was isolated and characterised by single-crystal X-ray diffraction studies. In contrast, l-tellurocystine, upon oxidation with H O , afforded Te and Te products. Zwitterionic organotellurolate(IV), [TeCl CH CH(NH )COOH] 13, was isolated and characterised by NMR and IR spectroscopy, mass spectrometry and elemental analysis. Compound 13 crystallizes in an orthorhombic space group. l-Tellurocystine, when reduced with NaBH , produced the desired tellurolate intermediate, which was trapped with bromoacetic acid. Furthermore, l- and d-tellurocysteine derivatives, [(RTeCH CH(NH )COOH) R=phenyl, substituted phenyl and naphthyl (24-39)] were synthesised and evaluated for their glutathione peroxidase (GPx)-like activities. The results show that l-tellurocysteine derivatives have higher activity than their D-tellurocysteine analogues. DFT calculations for l-tellurocysteine derivatives provided information about the bond lengths and bond angles. This study reveals that the introduction of naphthyl substituents (35-38) leads to twisted conformation of the amino acid derivatives.

Ultra-stable tellurium-doped carbon quantum dots for cell protection and near-infrared photodynamic application

“…The precursor, tellurocystine, was synthesized according to the literature [43]. Then tellurocystine (10 mg) was dissolved in deionized water (10 mL) at pH around 9 for good solubility.…”

gem-Heterosubstituted (stannyl)methylsilanes as synthetic equivalents of functionalized α-stannyl(methyl) anions

“…Organoselenides have been used as valuable synthetic intermediates, ligands, and catalysts. Furthermore, a growing number of selenium-containing small molecules has been recently demonstrated to possess an array of biological properties, including antioxidant, [23][24][25] anticancer, 26 and enzyme modulator activities. [27][28][29][30][31] The development of novel routes towards organoselenium derivatives is, therefore, highly desirable.…”

“…C NMR (CDCl3, 50 MHz), δ (ppm): 10.8, 13.7, 14.0, 27.3, 29.0, 38.4, 74.4, 125.3, 127.1, 128.2, 129.2, 131.0, 133.0, 142.9. MS: m/z (%) 260(35), 179 (79), 165(24), 102 (85), 91(26), 77 (100), 51 (51). Elemental analysis: C26H40OSeSn Calcd.…”

Chalcogen Bonds in Selenocysteine Seleninic Acid, a Functional GPx Constituent, and in Other Seleninic or Sulfinic Acid Derivatives

“…In this paper we describe the single crystal X‐ray structure of the selenocystinic acid ( 1 a ) (obtained through oxidation of L‐selenocystine with hydrogen peroxide, Scheme 2). [30,31] We show that the compound forms three Se ⋅⋅⋅ O short contacts [32] that seemingly affect the conformation and the overall packing in the crystal and can be rationalized as chalcogen bonds (ChBs) thanks to their directionality [33] . The ChB is the non‐covalent interaction wherein an element of group 16 of the periodic table functions as the electrophilic site [34] .…”