Novel microwave-assisted synthesis of the immunomodulator organotellurium compound ammonium trichloro(dioxoethylene-O,O')tellurate (AS101)

Synthesis and application of organotellurium compounds

Organotellurium compounds define the compounds containing carbon (organic group) and tellurium bond (C–Te). The first organic compound containing tellurium was prepared by Wohler in 1840 after the discovery of the metal by the Austrian chemist F. J. Muller von Reichenstein in the year 1782. The term tellurium was derived from Latin tellus. Tellurium was observed first time in ores mined in the gold districts of Transylvania. Naturally occurring tellurium compounds are present in various forms based on their oxidation states such as TeO2 (+4) and TeO3 (+6). These oxidation states of tellurium compounds are more stable as compared to the other oxidation states. Tellurium is a rare element and is considered a non-essential, toxic element. Tellurium possesses only one crystalline form which consists of a network of spiral chains similar to that of hexagonal selenium. Tellurium is used for the treatment and prevention of microbial infections prior to the development of antibiotics. Hence, the utilization of organotellurium compounds plays a significant role as reagents and intermediates in various organic syntheses.

Latest developments on the synthesis of bioactive organotellurium scaffolds

This review deals with the latest developments on the synthesis of biologically promising organotellurim scaffolds reported during last two decades.

Synergistic Combination of AS101 and Azidothymidine against Clinical Isolates of Carbapenem-Resistant Klebsiella pneumoniae

Owing to the over usage of carbapenems, carbapenem resistance has become a vital threat worldwide, and, thus, the World Health Organization announced the carbapenem-resistant Enterobacteriaceae (CRE) as the critical priority for antibiotic development in 2017. In the current situation, combination therapy would be one solution against CRE. Azidothymidine (AZT), a thymidine analog, has demonstrated its synergistically antibacterial activities with other antibiotics. The unexpected antimicrobial activity of the immunomodulator ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) has been reported against carbapenem-resistant Klebsiella pneumoniae (CRKP). Here, we sought to investigate the synergistic activity between AS101 and AZT against 12 CRKP clinical isolates. According to the gene detection results, the bla_OXA-1 (7/12, 58.3%)_, bla_DHA (7/12, 58.3%), and bla_KPC (7/12, 58.3%) genes were the most prevalent ESBL, AmpC, and carbapenemase genes, respectively. The checkerboard analysis demonstrated the remarkable synergism between AS101 and AZT, with the observable decrease in the MIC value for two agents and the fractional inhibitory concentration (FIC) index ≤0.5 in all strains. Hence, the combination of AS101 and azidothymidine could be a potential treatment option against CRKP for drug development.

Organotellurium compounds: an overview of synthetic methodologies

In wake of emerging applications of organotellurium compounds in biological and material science avenues, the current review describes their key synthetic methodologies while focusing the synthesis of organotellurium compounds through five ligand-to-metal linkages including carbon; carbon-oxygen; carbon-nitrogen; carbon-metal; carbon-sulfur to tellurium. In all of these linkages whether tellurium links with ligands through a complicated or simple pathways, it is often governed through electrophilic substitution reactions. The present study encompasses these major synthetic routes so as to acquire comprehensive understanding of synthetic organotellurium compounds.

Stability of antibacterial Te(IV) compounds: A combined experimental and computational study

Inorganic Te(IV) compounds are important cysteine protease inhibitors and antimicrobial agents; AS-101 [ammonium trichloro (dioxoethylene-O,O')tellurate] is the first compound of a family with formula NH₄[C₂H₄Cl₃O₂Te], where a Te(IV) centre is bound to a chelate ethylene glycol, and showed several protective therapeutic applications. This compound is lacking in stability performance and is subjected to hydrolysis reaction with displacement of the diol ligand. In this paper, we report the stability trend of a series of analogues complexes of AS-101 with generic formula NH₄[(RC₂H₃O₂)Cl₃Te], where R is an alkyl group with different chain length and different electronic properties, in order to find a correlation between structure and stability in aqueous-physiological conditions. The stability was studied in solution via multinuclear NMR spectroscopy (¹H, ¹³C, ¹²⁵Te) and computationally at the Density Functional Theory level with an explicit micro solvation model. The combined experimental and theoretical work highlights the essential role of the solvating environment and provides mechanistic insights into the complex decomposition reaction. Antimicrobial activity of the compounds was assessed against different bacterial strains.