Chemoenzymatic Synthesis and Antiherpes Activity of 5-Substituted 4,6-Difluorobenzimidazoles Ribo- and 2′-Deoxyribonucleosides

Abstract

A series of 5,6-disubstituted benzimidazole nucleosides, obtained earlier, did not show any significant antiviral activity at relatively low cytotoxicity in vitro. In the course of our research we have succeeded in introducing an additional fluorine atom into the benzimidazole ring system. A new series of 4,6-difluorobenzimidazoles, bearing various groups (fluoro-, methoxy-, ethoxy-, morpholino-, and pyrrolidino-) in the 5-position of the benzene ring, have been synthesized. All these compounds proved to be substrates for recombinant E. coli purine nucleoside phosphorylase (PNP) in the transglycosylation reaction. Effective methods for the synthesis of ribo-and 2′-deoxyribonucleosides with high yields (60-90%) have been described, and the formation of regioisomeric N3-nucleosides of benzimidazoles have been detected. The biological activity of the nucleosides obtained against herpes simplex virus type 1 (HSV-1) has been elucidated. All compounds show a low cytotoxicity in the cell culture Vero E6. 4,5,6-Trifluoro-1-(β-D-ribofuranosyl)benzimidazole and 5-methoxy-4,6-difluoro-1-(β-D-2′-deoxyribofuranosyl)benzimidazole proved to inhibit completely the progression of the virus cytopathic effect (CPE) at a multiplicity of infection (MOI) of 0.01 PFU/cell.

Chemoenzymatic Synthesis of Modified 2′-Deoxy-2′-fluoro-β-d-arabinofuranosyl Benzimidazoles and Evaluation of Their Activity Against Herpes Simplex Virus Type 1

“…Selectivity index (ratio of cytotoxicity and antiviral activity levels against simplex virus type 1 herpes) was varied from 0.00 (8a) to 9 (8d) (see Table 4). 10,14 Arabinose-1-α-phosphate and 1-(β-D-arabinofuranosyl)uracil were used as sugar donors for β-D-arabinosides synthesis. However, we did not succeed in synthesizing nucleosides, while benzimidazole nucleosides 6 and 7 and arabinose-1-α-phosphate discretely are excellent substrates for purine nucleoside phosphorylase (PNP) from E. сoli.…”

“…18,19 In a patent, 20 the synthesis of 2,5,6-trichloro-1-(β-D-arabinofuranosyl)benzimidazole from 2,5,6-trichloro-1-(2,3,5-tri-O-benzyl-β-D-arabinofuranosyl)benzimidazole was described, but the structure of this compound was not established. Our approach to the synthesis of 1-(β-D-arabinosyl)benzimidazole (14) is shown in Scheme 1. The scheme illustrates only the transformation of furanoside form, while in fact there was a mixture of pyranoside and furanoside at all stages.…”

“…The first step of the synthesis is alkylation of arabinose (9) with methoxymethyl chloride (MOMCl) (Scheme 1). The reaction results in the formation of a complex mixture of (14), which can be separated easily by HPLC.…”

“…26 Modified benzimidazoles 8a-d were obtained according to the previously reported procedures. 10,11,14 To optimize the reaction conditions we have determined optimal ratio between 15 and 8a-d, as well as the optimal amount of PNP. The reactions were performed at 50 °C in water (pH 7) and monitored by reversed-phase…”

“…Meanwhile, the synthesis of ribosides and 2′-deoxyribosides 7 proceeds even at pH 4.0 and 10.0 (but much slower). 14…”