In a screening program using-the agar diffusion-plaque inhibition test, 22 out of 27 substituted aminopyrazoles tested showed marked antiviral activity against mengovirus in FL cell cultures. The efficacy of the different derivatives was compared by determining their effect on the yield of infectious virus after a one-step growth cycle. The antiviral activity against mengovirus correlated with the chain length of the substituents and increased or decreased according to the position of the side chain.Our studies are concerned with pyrazolo- [3,4-d]pyrimidines, which were synthesized to be possible purine antagonists and, in this context, to exhibit antiviral activity. In the course of these studies we found that even the 5-amino-4-cyanopyrazoles (Fig. 1I) 49/20, 1974). So far little is known about the antiviral activity of pyrazolo-[3,4-dipyrimidines. Roby et al. (3) tested 1-H pyrazolo-[3,4-d]pyrimidine on myxoma and fibroma viruses in vitro but did not find antiviral activity. Antiviral effects of substituted 5-amino-4-cyanopyrazoles of structure I (Fig. 1) have not been described yet. However, this class of compounds bears a slight resemblance to Ribavirin (Virazole) (Fig. 1II), an agent recently reported to exhibit broad-spectrum antiviral activity (8), as well as to the antiviral antibiotic Pyrazomycin ( Fig. 1III) , 158th, 1969, abstr. 38). Furthermore, there are structural relationships among compounds with structure I and the cytostatic agents 5-amino-13-D-ribofuranosyl-pyrazole-4-carboxamidine (Fig. lIV) (1) and 5-amino-l,3-D-ribofuranosyl-1,2,3-triazole-4-carboxamidine ( Fig. 1V) (1).The aim of the present study was to elucidate structure-activity relationships by variation of structure I substituents R,, R2, and R%, using the model mengovirus-FL cells in vitro. MATERIALS AND METHODSCell cultures. FL cells, media, and the cultivation of the cells were previously described (5).Virus. A plaque-purified strain of mengovirus selected to grow on FL cells was used (5). Screening method. The agar diffusion-plaque inhibition test described by Tonew and Tonew (4, 5) was used. A cell monolayer (4 x 106 to 5 x 106f cells) was infected with a concentration of approximately 200 plaque-forming units per bottle of virus, unadsorbed virus was removed, and the cell sheet was overlaid with agar. Standard sized paper disks (Schleicher and Schull [Dassel/Einbeck, FRG]; diameter, 6 mm) containing test compounds were placed on the agar. After 2 days of incubation at 37 C and staining with neutral red, plaque-free areas were recorded.The therapeutic index was estimated by using different concentrations (50 mM and lower) of compounds and determining the quotients of the maximally tolerated and the minimally active concentrations.Determination of effect of test substances on infectious virus yield. Cultures of FL cells (tubes with 4 x 105 cells) were infected with 20 mean tissue culture infective doses of mengovirus per cell. After 40 min of adsorption at 37 C, the residual unadsorbed virus was removed, cells were washed th...

Antiphytoviral compounds with noncyclic azine structutre The antiphytoviral activities of variously substituted compounds with noncylic azine structures have been studied f a total of 90 tested compunds 42 had the effect of more or less strong inhibiting the concentration of potato virus X (PVX) in inoculated and / or secondarily infected leaves of Nicotiana tabacum L. cv Samsun (Table.1) An effect on the virion of PVX in vitro couldn't be observed (Table.2) Thus the substances may interact with the virus replication. Some of them also reduced the number of local lesions caused by tabacco mosaic virus on leaves of Nicotiana glutinosa L. (Table‐3) Several Compounds proved exellent synergists of 2,4‐ dioxohexahydro‐ 1,3,5‐ triazine (DHT = 5 azadihydrouracil; Table 4) Pyridine‐ 3‐ aldehyde S ethyl isothiosemicarbazone and the Cu complex of 1‐ ethyl‐isatine S‐ ethyl isothisosemicarbazone when used in combination with 2,4 dioxohexahydro‐ 1,3,5, triazine, greatly increased the mass of potato tubers produced from plantlets grown up from patato eye cutting as compared with the indentical control Simultaneously the mentioned substances reduced the number of symptom bearing eye cutting plants Quinoline 2‐ aldehyde‐ N‐ oxide S‐ allyl‐isothiosemicarbazone had the effect of very greatly reducing the number of symptom‐bearing plants without substantially influencing the mass of tubers (Table 5). Thus some compounds with noncyclic azine structure especially when used in combinitation with DHT, may be of high interest for practical application Comparing the structures of compounds with noncyclic azine structure active against plant or human viruses it should be noted that antiphytoviral compounds active in these two different virus host systems often are closely related structurally.

Aus dem Dinitrochlorbenzol (I) werden über die Dinitraniline (III) die Nitro‐ und Aminobenzimidazole (VII) und (VIII) hergestellt und mit Isocyanaten, Isothiocyanaten und Aldehyden umgesetzt.