Ganapathi R. Revankar

Inhibition of human cytomegalovirus in culture by alkenyl guanine analogs of the thiazolo[4,5-d]pyrimidine ring system.

A series of alkyl and alkenyl guanine analogs containing a thiazolo[4,5-d]pyrimidine ring system were prepared by reaction of the appropriate alkyl halide with the sodium salt of the heterocycle. In preliminary antiviral efficacy evaluations against laboratory strains of both human cytomegalovirus (HCMV) and herpes simplex virus types 1 and 2, it was determined that two of the compounds (T70072 and T01132) were more active and less toxic in stationary-phase cell monolayers than were the other derivatives tested. T01132 and T70072, which have 2-pentenyl and 3-methyl-2-butenyl moieties attached to position 3 of the 5-aminothiazolo[4,5-d]pyrimidine-2,7-dione, respectively, were then more extensively evaluated for anti-HCMV activity. The concentrations of T01132 and T70072 required to inhibit HCMV by 50% in plaque reduction assays were approximately 0.5 and 6.8 microM, respectively. These two compounds inhibited the growth of KB, MRC-5, or Vero cells at concentrations of 75 to 150 microM, depending upon the cell line. In bone marrow progenitor cells T01132 was slightly less toxic than ganciclovir (DHPG). The 50% inhibitory concentrations of T01132 against clinical isolates and DHPG-resistant strains of HCMV were approximately the same as those obtained for laboratory strains of HCMV (approximately 0.5 microM). When tested in combination with DHPG, the resultant antiviral activity was determined to be additive but not synergistic. Experiments performed using variations of the viral multiplicity of infection (MOI) demonstrated that T01132 was more active than DHPG at a low MOI (0.002 or 0.02). However, when a higher MOI (0.2 or 2.0) was used, DHPG was more efficacious than T01132. In experiments in which drug was added at various times post-viral infection, T01132 was most effective when added within the first 24 h post-HCMV infection while DHPG was able to protect cells in this assay system when added up to 48 h postinfection, indicating that T01132 is exerting its antiviral effect on events leading up to and possibly including viral DNA synthesis. The data presented in this report suggest that the antiviral activity of alkenyl-substituted thiazolopyrimidine derivatives may represent a mechanism of action against herpesviruses alternative to that of classical nucleoside analogs such as acyclovir or DHPG.

A facile synthesis of tubercidin and related 7-deazapurine nucleosides via the stereospecific sodium salt glycosylation procedure

Abstract A facile high-yield synthesis of 7-deazaadenosine (tubercidin, 5 ), 7-deazaguanosine ( 10 ), 2′-deoxy-7-deaza-6-thioguanosine ( 12 ) and 2′-deoxy-7-deazaguanosine ( 15 ) by the regioselective and stereospecific sodium salt glycosylation procedure is described.

A convenient synthesis of 5′-deoxyribonucleosides

Abstract A facile, two-step synthesis has been devised for the chemical preparation of 5′-deoxyribonucleosides from the parent nucleosides via the 5′-chloro-5′-deoxy-nucleosides. Treatment of 5′-chloro-5′-deoxynucleosides with tributyltin hydride and α,α′-azobis(isobutyronitrile) in dry tetrahydrofuran yields the corresponding 5′-deoxy-nucleosides. Dechlorination of 5′-chloro-5′-deoxythymidine with tributyltin hydride gives 1-(2,5-dideoxy-β- D - erythro -pentofuranosyl)thymine (5′-deoxythymidine) in good yield. Similarly, dechlorination of 9-(3,5-dichloro-2,3,5-trideoxy-β- D - threo -pentofuranosyl)adenine and 1-(3,5-dichloro-2,3,5-trideoxy-β- D - threo -pentofuranosyl)thymine yields the corresponding two trideoxynucleosides.

A novel synthesis of S6-cyanoethyl-2′-deoxy-6-thioguanosine and its incorporation into triple helix forming oligonucleotides☆

Abstract A simple and expeditious synthesis of S 6 -cyanoethyl-2′-deoxy-6-thioguanosine from 2′-deoxyguanosine has been accomplished in good yield and incorporated into several triple helix forming oligonucleotides using the solid-phase phosphoramidite chemistry.

Efficacy of 9-β-d-Arabinofuranosylhypoxanthine 5′-Monophosphate in Therapy of Equine Abortion Virus-Induced Hepatitis in Hamsters

Equine abortion virus (EAV)-induced hepatitis in hamsters presents an interesting animal model for the evaluation of drugs possessing anti-deoxyribonucleic acid virus activity. These experiments demonstrate that 9-β-d-arabinofuranosylhypoxanthine 5′-monophosphate (ara-HxMP), a new synthetic, water-soluble, antiviral agent, effectively controls this disease in hamsters with a therapeutic index of ∼60. Ara-HxMP prevented hepatitis-associated deaths in hamsters, reduced the titer of EAV developing in hamsters, and inhibited the increase of serum glutamic pyruvic transaminase in EAV-infected hamsters.

Broad-spectrum activity of 8-chloro-7-deazaguanosine against RNA virus infections in mice and rats

Abstract A novel nucleoside analog, 8-chloro-7-deazaguanosine (8-Cl-7-dzGuo), was evaluated for anti-RNA virus activity in rodents in parallel with the related compound 7-deaza-7-thia-8-oxoguanosine (7-dzTOGuo). Half-daily intraperitoneal (i.p.) doses of each substance administered 24 and 18 h prior to i.p. virus challenge protected the majority of mice infected with banzi, encephalomyocarditis, San Angelo, and Semliki Forest viruses at doses of 25, 50 and 100 mg/kg/day. These compounds at 100 mg/kg/day also protected most suckling rats infected intranasally with rat coronavirus. However, no survival benefit was afforded to treated mice infected intranasally with vesicular stomatitis virus. 8-Cl-7-dzguo was orally active against Semliki Forest virus in mice at 200 and 400 mg/kg/day, whereas 7-dzTOGuo is reported to not be effective orally. In uninfected mice, the two compounds induced similar amounts of interferon following i.p. injections. Interferon was induced by oral treatments with 8-Cl-7-dzGuo but not with 7-dzTOGuo. Fifty percent acute lethal doses to uninfected mice treated i.p. in half-daily doses for one day with 7-deazaguanosine (7-dzGuo), 7-dzTOGuo, and 8-Cl-7-dzGuo were 400, 600 and > 1600 (no mortality at this dose) mg/kg/day, respectively. Daily, i.p. treatments for 14 days with these substances (100 mg/kg/day) showed 7-dzGuo as 100% lethal and the other two substances at not toxic. By virtue of reduced toxicity and oral bioavailability, 8-Cl-7-dzGuo appears to have the greatest clinical potential as an interferon-inducing antiviral agent.

A total synthesis of 2'-deoxy-9-deazaguanosine (9-deaza-dG) and its incorporation into triple helix forming oligodeoxyribonucleotides with antiparallel motif

Abstract A simple synthesis of 2-amino-7-(2-deoxy-β-D- erythro -pentofuranosyl)pyrrolo-[3,2- d ]pyrimidin-4(3 H )-one (9-deaza-dG) has been achieved and it has been incorporated into triplex forming oligonucleotides using the solid-support, phosphoramidite chemistry. 9-Deaza-dG is effective in preventing the formation of G-tetrads in G-rich oligonucleotides.

Immunoenhancing properties and antiviral activity of 7-deazaguanosine in mice.

The nucleotide analog 7-deazaguanosine has not previously been reported to possess biological (antiviral or antitumor) properties in cell culture or in vivo. Up to 10(5) U of interferon per ml was detected in mouse sera 1 to 4 h following oral (200-mg/kg of body weight) and intraperitoneal (50-mg/kg) doses of the compound. 7-Deazaguanosine also caused significant activation of natural killer and phagocytic cells but did not augment T- and B-cell blastogenesis. Intraperitoneal treatments of 50, 100, and 200 mg/kg/day administered 24 and 18 h before virus inoculation were highly protective in mice inoculated with lethal doses of Semliki Forest or San Angelo viruses. Less but still significant survivor increases were evident in treated mice infected with banzi or encephalomyocarditis viruses. In most cases, the degree of antiviral activity was similar to that exhibited by the biological response modifier 7-thia-8-oxoguanosine. 7-Thia-8-oxoguanosine was more potent than 7-deazaguanosine against encephalomyocarditis virus in mice, however. Oral efficacy was achieved with 7-deazaguanosine treatments of greater than or equal to 100 mg/kg against all virus infections, whereas 7-thia-8-oxoguanosine is reported to be devoid of oral activity in rodents. Thus, 7-deazaguanosine represents the first reported orally active nucleoside biological response modifier exhibiting broad-spectrum antiviral activity against particular types of RNA viruses.

Design of Nucleoside Analogs as Potential Antiviral Agents

Viruses are composed of either RNA or DNA, encased in protein shells and often further wrapped in lipid-containing envelopes. Viruses multiply only within living cells, commandeering the host cell to synthesize viral proteins and viral nucleic acids followed by final assembly into new virion particles. Viral infection may vary in severity from mild and transitory infections to illnesses that terminate in death. Persistent viral infection, which for years may not be accompanied by symptoms, can eventually cause chronic degenerative diseases with fatal outcome. It is known that viruses cause certain cancers in animals and man. Successful treatment of viral diseases with antiviral agents requires interruption of virus multiplication by specific inhibition of viral enzymes.

Synthesis of Certain Acyclic Nucleoside Analogs of 1,2,4-Triazolo[3,4-f][1,2,4]triazine and Pyrimido[5,4-d]pyrimidine

Abstract Synthesis of 2-penten-1-yl (8a) and ganciclovir analog (8b) of 1,2,4-triazolo[3,4-f][1,2,4]triazine was accomplished by the ring annulation of the corresponding hydrazides (6a and 6b), which in turn was obtained by the dehydrative coupling of 4 with 5a or 5b. Base catalysed ring expansion of N9-alkylpurine-6-carbonitriles (10a 10c 10e) provided the acyclic analogs of 4-aminopyrimido-[5,4-d]pyrimidines (13a 13d 13e). Debenzylation of 13e afforded the ganciclovir analog (13f) of 4-amino-8-(β-D-ribofuranosylamino)-pyrimido[5,4-d]pyrimidine. However, compound 10b did not undergo the expected rearrangement but resulted in the formation of the methyl formimidate derivative (12).