The synthesis and antiviral activity of 1-(4-сhlorophenyl)- 4-(para-tolyl)-5,6,7,8-tetrahydro-2а,4a-diazacyclopenta[cd]- azulene-2-carboxylic acid derivatives

Aim. To synthesize, prove the structural framework and study the antiviral activity of 1-(4-chlorophenyl)4-(para-tolyl)-5,6,7,8-tetrahydro-2a,4a-diazacyclopenta[cd]azulene-2-carboxylic acid derivatives. Results and discussion. The antiviral activity of 1-(4-chlorophenyl)-4-(para-tolyl)-5,6,7,8-tetrahydro-2a,4adiazacyclopenta[cd]azulene-2-carboxylic acid (4-methoxyphenyl)amide was determined in the Southern Research Institute (SRI, Birmingham, Alabama). The efficacy of this compound was expressed by EC50, IC50 and SI values determined in vitro within a range of concentrations of 0.1 – 100 μg/mL. The antiviral drug Ribavirin (Sigma) and the active substance of Amizon – 4-(N-benzyl)aminocarbonyl-1-methylpyridinium iodide were used as the reference drugs. Experimental part. Condensation of 2-methoxy-3,4,5,6-tetrahydro-7H-azepine with α-amino-4-methylacetophenone hydrochloride led to 3-(4-methylphenyl)-6,7,8,9-tetrahydro-5H-imidazo[1,2-a]azepine. By boiling the latter with α-bromo-4-chloroacetophenone in ethyl acetate 1-[2-(4-chlorophenyl)-2-oxoethyl]-3-(para-tolyl)-6,7,8,9-tetrahydro-5H-imidazo[1,2-a]azepin-1-ium bromide was isolated, which in aqueous alkali solution was converted into 1-(4-chlorophenyl)-4-(para-tolyl)-5,6,7,8-tetrahydro-2а,4a-diazacyclopenta[cd]azulene. The latter while reacting with the corresponding aryliso(thio)cyanates in a dry benzene gave 1-(4-chlorophenyl)-4-(para-tolyl)-5,6,7,8-tetrahydro-2a,4a-diazacyclopenta[cd]azulene-2-carboxylic acid (thio)amides. 1H NMR-spectra for the compounds synthesized were recorded on a Bruker VXR-300 spectrometer (Germany) with the operating frequency of 299.945 MHz, and also on a Bruker DRX300 (Germany) spectrometer with the operating frequency of 500.13 MHz, in DMSO-d6 using tetramethylsilane (TMS) as an internal standard. The melting points were measured using a RNMK 05 apparatus (VEB Analytik, Dresden). Conclusions. The series of new 1-(4-chlorophenyl)-4-(para-tolyl)-5,6,7,8-tetrahydro-2a,4a-diazacyclopenta[cd]azulene-2-carboxylic acid (thio)amides has been synthesized. The antiviral activity of 1-(4-chlorophenyl)4-(para-tolyl)-5,6,7,8-tetrahydro-2a,4a-diazacyclopenta[cd]azulene-2-carboxylic acid (4-methoxyphenyl)amide has been studied in the Southern American Research Institute (SRI, Birmingham, Alabama), and the high level of the antiviral activity has been found against Flu A H1N1 California/07/2009 virus.

During this period, 1128 of those lethal cases were registered in Ukraine. Over 80 % of deaths from influenza characterizing the Californian strain were registered in the age category of 18 -50 years.
At the background of accompanying conditions (obesity, diabetes, chronic lung diseases, cardiovascular diseases, etc.) the fatal double hemorrhagic pneumonia is reliably observed [3].
Flu A H1N1 virus was first discovered in 1931 by the American scientist Richard Shope, and was later classified as endemic zoonosis [5,6].
The strain of pandemic H1N1 ("Pandemic (H1N1) 09 Virus") became known as "Swine Influenza" in media [1]. A/California/04/2009 (H1N1) and A/Cali- Modern antiviral medications are classified by the mechanism of action as those that directly damage the replication of virus, and those that modulate the immune system of the host organism. The group of drugs of this action registered and allowed to use in Ukraine includes Amizon, Amantadin, Arbidol, Zanamivir, Inozin pranobecs, Ozeltamivir, Rimantadin, etc. [8 -15].
In Ukraine for curing conditions caused by the strain of H1N1 virus, 4-(N-benzyl)aminocarbonyl-1-methylpiridinium iodide (Amizon) is currently used. It was developed by the Institute of Pharmacology and Toxicology of Ukraine. Amizon possesses the anti-inflammatory, analgesic and antipyretic effects [11]. The analgesic effect is manifested with participation of the reticular formation of the brain stem [12]. Amizon has interferonogenic properties, causes the inhibiting effect on influenza viruses, and increases the body resistance to viral infections [14]. All these make Amizon a promising drug for prevention and treating different virus diseases [13].
However, from position of evidence-based medicine, there is no single opinion regarding indubitable effectiveness of certain drugs (Arbidol, Amixin, Amizon, Kagocel, Immunofam, etc.) used as immunomodulators with the anti-influenza activity [15]. Therefore, the search for new antiviral compounds is still relevant.
Among the side effects of Ribavirin there is dosedependent anemia. In the case of kidney, cardiovascular diseases, this medication must be used only after thorough examination [17], which makes search for new antiviral compounds even more relevant. The results obtained indicate that the antiviral activity of 1-(4-сhlorophenyl)-4-(para-tolyl)-5,6,7,8tetrahydro-2а,4а-diazacyclopenta[cd]azulene-2-carboxylic acid (4-methoxyphenyl)amide 9d is observed in 2.56 times lower dose than that for Ribavirin substance and in 13.8 times lower dose than for Amizon substance. The selectivity index of the compound under research appeared to be more than 29 and IC 50 > 100 μg/mL. At the same time, the selectivity index of Ribavirin was more than 37 and IC 50 > 320 μg/mL. It should be noted that if IC 50 for those two compounds was the same, then SI for amide 9d would be three times higher and would be equal to SI > 92.8.
The melting points were measured on a smallsized heating table with a RNMK 05 observation device (VEB Analytik, Dresden). Notes: EC 50 -the effective concentration determined by the dose/effect curve, and is a compound concentration, in which effect is observed in 50 % of the population after a definite period of time passed, μg/mL; IC 50 -the concentration, in which inhibition of cells by a compound is 50 %, μg/mL; SI -the index of selectivity, which is the indicator of the compound efficacy, expressed in ІС 50 to ЕС 50 ratio