Design, synthesis and antiviral activity of novel 4,5-disubstituted 7-(β-D-ribofuranosyl)pyrrolo[2,3-d][1,2,3]triazines and the novel 3-amino-5-methyl-1-(β-D-ribofuranosyl)- and 3-amino-5-methyl-1-(2-deoxy-β-D-ribofuranosyl)-1,5-dihydro-1,4,5,6,7,8-hexa-azaacenaphthylene as analogues of triciribine

The synthesis of several heterocyclic analogues of the biologically important nucleoside antibiotic toyocamycin and the tricyclic nucleoside triciribine (TCN) were prepared along with their 2'-deoxy counterparts. Coupling of 2-nitropyrrole-3,4-dicarboxamide (15) under a variety of conditions with alpha-chloro-2-deoxy-3,4-di-O-toluoyl-D-ribofuranose (16a) gave mixtures of the alpha and beta anomers. A coupling of 15 with 1-chloro-2,3,5-tri-O-benzoyl-D-ribofuranose (18) gave exclusively the beta anomer. Individually, the two pyrrole nucleosides were treated with Pd/C, H-2 to reduce the nitro groups and cyclized with nitrous acid, and the corresponding 4-position was functionalized as a triazoyl derivative. Nucleophillic displacement was carried out with ammonia to give a mixture of 4-amino-1-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)pyrrolo[2,3-d]-[1,2,3]triazine-5-carbonitrile (26) and 2-amino-1-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)pyrrole3,4-dicarbonitrile (27), the latter being formed via a retro-Diels-Alder reaction. The subsequent addition of hydrogen sulfide, water, methanol, hydroxylamine, cyanamide, hydrazine and methylhydrazine to the 5-cyano group was carried out to give the corresponding analogues. In the case of methyl hydrazine, subsequent treatment with NaOMe in methanol gave the title hexaazaacenaphthylenes. Biological evaluation of the compounds established that the pyrrole (17 beta, 19-21) and most of the pyrrolotriazine (22, 24, 28, 32-34) nucleosides were inactive or weakly active against human cytomegalovirus (HCMV) and herpes simplex virus type 1 (HSV-1). In contrast 29 and 31 were active against one or both of these viruses but activity was poorly separated from cytotoxicity. In contrast, the 2-aza analogue of sangivamycin (30) was active against HCMV and HSV-1 but this apparent activity was most likely due to its high cytotoxicity. The tricyclic nucleoside 12, was active against its target virus, human immunodeficiency virus type 1 (HIV-1), but this activity was not well separated from cytotoxicity.