Radical Dehalogenation and Purine Nucleoside Phosphorylase E. coli: How Does an Admixture of 2′,3′-Anhydroinosine Hinder 2-fluoro-cordycepin Synthesis

Abstract

During the preparative synthesis of 2-fluorocordycepin from 2-fluoroadenosine and 3′-deoxyinosine catalyzed by E. coli purine nucleoside phosphorylase, a slowdown of the reaction and decrease of yield down to 5% were encountered. An unknown nucleoside was found in the reaction mixture and its structure was established. This nucleoside is formed from the admixture of 2′,3′-anhydroinosine, a byproduct in the preparation of 3-′deoxyinosine. Moreover, 2′,3′-anhydroinosine forms during radical dehalogenation of 9-(2′,5′-di-O-acetyl-3′-bromo- -3′-deoxyxylofuranosyl)hypoxanthine, a precursor of 3′-deoxyinosine in chemical synthesis. The products of 2′,3′-anhydroinosine hydrolysis inhibit the formation of 1-phospho-3-deoxyribose during the synthesis of 2-fluorocordycepin. The progress of 2′,3′-anhydroinosine hydrolysis was investigated. The reactions were performed in D2O instead of H2O; this allowed accumulating intermediate substances in sufficient quantities. Two intermediates were isolated and their structures were confirmed by mass and NMR spectroscopy. A mechanism of 2′,3′-anhydroinosine hydrolysis in D2O is fully determined for the first time.

Biotechnological and Biomedical Applications of Enzymes Involved in the Synthesis of Nucleosides and Nucleotides

“…In the biocatalysis section, glycosyltransferases are the most cited enzymes, and several authors focus their attention on this enzyme family. In this respect, Kayushin et al [8] developed the preparative synthesis of 2-fluorocordycepin from 2-fluoroadenosine and 3deoxyinosine catalyzed by purine nucleoside phosphorylase from E. coli but also explored the presence of by-products in this process, providing new insights about this undesirable effect. Similarly, Rivero et al performed the sustainable production of cladribine (an FDAapproved anticancer agent) by a novel 2 -deoxyribosyltransferase (NDT)-based biocatalyst, including a covalent immobilization of Lactobacillus delbrueckii 2 -deoxyribosyltransferase (LdNDT) onto glutaraldehyde-activated biomimetic silica nanoparticles followed by biocatalyst entrapment in calcium alginate [9].…”