122970-56-3

Compounds of the structure: STR1 wherein R4, R5, R6 and R7 individually are H, OH or C1 -C18 O-acyl and R3 is H, C1 -C18 acyl or STR2 or R5 and R7 are H or OH, R6 is H and together R3 and R4 are STR3 and X is =O or =S; Y is --OH, --SH, --Nh2 or halogen; and Z is H , --Nh2, --OH or halogen; wherein halogen is Cl or Br; or pharmaceutically acceptable salt thereof are useful as antivirals, antitumors, antimetastatics and as immune system enhancers.

Novel analogues of the naturally occurring purine nucleosides were synthesized in the thiazolo[4,5-d]pyrimidine ring system to determine the immunomodulatory effects of insertion of a sulfur atom in place of nitrogen at position 7 of the purine ring. In particular, 5-amino-3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (7, guanosine analogue), 3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H)-trione (8, xanthosine analogue), 3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (10, inosine analogue), and 7-amino-3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2(3H)-one (32, adenosine analogue) were prepared, as well as the 8-mercaptoguanosine (14) and 6-mercaptoguanosine (17) analogues. Single-crystal X-ray studies confirmed the structural assignment of 17 and 32 as having the β-configuration with the site of glycosylation at N3. The nucleosides were evaluated for their ability to potentiate various murine immune functions in direct comparison to the known active agents 8-bromoguanosine (1), 8-mercaptoguanosine (2), and 7-methyl-8-oxoguanosine (3). Two of the guanosine analogues, 7 and 14, were found to exhibit significant immunoactivity relative to the positive control compounds (1-3), while the adenosine, inosine, xanthosine, and 6-mercaptoguanosine analogues were devoid of activity. Compound 7 exhibited greater immunoreactivity than any of the other guanosine analogues and derivatives in all test systems. Specifically, 7 was shown to be about twice as potent as 3 in the murine spleen cell mitogenicity assay. In addition, treatment with 7 produced about a 4-fold increase in natural killer cell cytotoxicity, while treatment with 3 afforded a 3-fold increase over controls. Finally, 7 provided excellent protection (92% survivors compared to 0% for placebo controls) against Semliki Forest virus in mice. Induction of interferon may account for the major mode of action of these guanosine analogues.

Compounds of the structure: STR1 wherein R 1 and R 2 individually are H or C 1 -C 18 acyl and R 3 is H, C 1 -C 18 acyl or STR2 or R 1 is H and together R 2 and R 3 are STR3 and X is O or S, Y is --OH, --SH, --NH 2 or halogen, and Z is H, --NH 2, --OH or halogen, wherein halogen is Cl or Br, or a pharmaceutically acceptable salt thereof are useful as antivirals, antitumors and as immune system enhancers.