The redox transformations and nucleophilic replacements as possible metabolic reactions of the drug “Triazaverin”. The chemical modeling of the metabolic processes

As a model of metabolic transformations of antiviral drug “Triazaverin” and its analogues-2-alkylthio-6-nitro-1,2,4-triazolo[5,1-c][1,2,4]triazine-7-ones 1a-d examined the oxidation of alkylthio groups to the corresponding sulfoxides 2a-d and sulfones 3a-d, as well as the process of nucleophilic substitution sulfonyloxy group of cysteine and cysteamine with the formation of compounds 5 and 6.


introduction
The relevance of creating new antiviral drugs due to the joint action of such operating factors as the spread of socially significant, particularly dangerous infections, and the emergence of pathogenic viral strains resistant to existing drugs.
The antiviral drug "Triazaverin" and its analogues are highly effective in experiments in vivo and decreased activity in experiments on cell cultures, suggesting that the antiviral effect is not the "Triazaverin", and products of its transformations in the body.One way to identify such transformations in the organism is to predict the possible products of modifications of the compounds and chemical synthesis models.
Based on the molecular structure of compounds 1a and study of chemi-DOI: 10.15826/chimtech.2015.2.3.025№ 3 | 2015 Chimica Techno Acta cal properties of nitroazolo [5,1-c] [1,2,4] triazines [1] can assume various variants of metabolism: redox transformations in the body (directions A, B) as the reduction of the nitro group under the action of a reductases (direction A), oxidation of alkylthio fragment under the action of oxidases (direction B) and its further transformation.The part transferases under the action of N -and S-nucleophils, such as lysine, arginine, cysteine could lead to the replacement of alkylthio-or nitro groups (directions C, D).
The hydrolytic enzymes are also quite capable to lead the transformation of "Tri-azaverin" accompanying the degradation of triazine cycle with the break of bond C-N (direction E).The alkylation on the N-atom is possible too (direction F).
With regard to the redox transformations of "Triazaverin" that we previously established that after the intragastric administration of laboratory animals of the drug substance, there is a reduction of the nitro group with the formation of 2-methylthio-6-amino-1,2,4-triazolo[5,1c][1,2,4]triazine-7-one [2], does not exhibit antiviral action in vitro and, most likely, which is not applicable metabolite.

Results and Discussion
Considering the possibility of oxidation of alkylthio groups under use "Triazaverin" and its analogues, it should be noted that in the majority of viral infections at an early stage of the process is increased generation of reactive oxygen species [3].Based on the foregoing, it is natural to assume that in these conditions can occur in the oxidation reaction of S-methyl group of "Triazaverin" characteristic, for example, for SH-containing amino acids of methionine under oxidative stress.
In the present communication present data on the production model experiments with the drug "Triazaverin" -the study of the oxidation of S-methyl group and the behavior of oxidation products under the action of S-nucleophils.This approach allows, on the one hand, to pre-dict the course of chemical reactions related to the behavior of the drug in the body, and on the other hand, by the synthesis of the respective compounds to simulate the process of formation of covalent bonds of azolo[5,1-c]1,2,4-triazines with S-key fragments of proteins as cells and virus.

Redox-transformations of "Triazaverin" and its derivatives
The first aspect of this work was the synthesis of model compounds -oxidation of sulfhydryl groups in molecules of sodium salts of 2-alkylthio-6-nitro-1,2,4-triazolo[5,1-c]1,2,4-triazine-7-ones 1a-d or in the associated N-H-acids comprising the formation of heterocyclic sulfoxides 3a-d and sulfones 4a-d.Sulfoxides The redox transformations and nucleophilic replacements as possible metabolic reactions of the drug "Triazaverin".The chemical modeling of the metabolic processes № 3 | 2015 Chimica Techno Acta 3a-d (Scheme 1) were obtained under the treatment of the compounds 1a-d or 2a-d by the equimolar quantity of 18 % hydrogen peroxide in the trifluoroacetic acid.
Further oxidation to the corresponding sulfones 4a-d with the yields 62-71 % carried out by gradual addition of excess 2.2 equivalent of 30 % hydrogen peroxide to the suspension of 2-alkylthio-1,2,4triazolo[5,1-c]-triazines in the trifluoroacetic acid at room temperature.
The represented reactions model the possible metabolic transformations of "Triazaverin" and its derivatives under the action of the active forms of oxygen including hydrogen peroxide.
Nucleophilic replacement of methylsulfonilic group.It is known that alkylsulfonyl fragments are susceptible to the substitution reactions when interacting with nucleophiles [4].With regard to the behavior of nitro group in "Triazaverin" but the susceptibility of the nitro group associated with aromatic (heteroaromatic) cycle to the displacement under the nucleophiles [5] is well known.
Thus in the structure of 2-alkylsulfonyl-1,2,4-triazolo[5,1-c]1,2,4-triazine-7-ones 4a-d there are two groups that are susceptible to nucleophilic displacement.This situation is of interest for the research of the comparative reactive ability of the easy outgoing groups CH 3 SO 2in 1,2,4-triazole and NO 2 in1,2,4-triazine cycles in the compounds 4a-d and also as the model of the behavior of "Triazaverin" in the organism.As the nucleophilic reagents in this work were used S-nucleophiles(cysteine and cysteamine), which can be regarded as models of protein fragments containing cysteine fragment.
The date of NMR 1 H, IR-spectroscopy and elemental analysis for the compounds 5, 6 correspond to the attributed structures.
The described displacement of alkylsulfonyl group in the compound 4a is the argument in favor of the assumption about the possible participation of this fragment in the metabolic transformations of "Triazaverin".Elemental analyses were performed on CHNS-analyzer "Perkin Elmer 2400-II".IR spectra (4000-400 cm -1 ) of the received compounds were recorded on a spectrophotometer "Perkin Elmer Spectrum One BFTIR" in thin layer of a To a suspension 0.01 mol of sodium salt 2-alkylthio-6-nitro-1,2,4triazolo[5,1-c]1,2,4-triazin-7-one (1) in 10 mL of trifluoroacetic acid by mixing was added 1.78 ml (1 eq.) of 18 % hydrogen peroxide.The reaction mass is mixed at room temperature during 3 hours.The resulting solid precipitate was filtered and was crystallized from iso-propanol.

NMR 1 H
and 13 C spectra were recorded on a spectrometer Bruker DRX-400 (400 and 100 MHz, respectively) in DMSO-d 6 and D 2 O.The chemical shifts are recorded in σ scale relatively internal standard TMS for NMR 1 H spectra.