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The P2 family of membrane-bound receptors is activated by naturally occurring nucleotides. When activated, these widely distributed receptors elicit cellular signaling which mediate multiple tissue-specific effects throughout the body. P2X receptors are ligand-gated ionotropic channels, while P2Y receptors belong to the superfamily of metabotropic G protein-coupled receptors. To date, there are six human cloned and functionally characterized subtypes of the P2Y family: P2Y1, P2Y2, P2Y4, P2Y6, P2Y11 and P2Y12. There exists enough agonist specificity between receptor subtypes to allow functional identification of newly found putative receptors. There are few specific antagonists of the P2Y receptors.

A series of dinucleoside 5-polyphosphates UpnU (n = 2-7) was synthesized. Their relative potencies as agonists at the G-protein-coupled receptors P2Y1, P2Y2, P2Y4, and P2Y6 were determined by intracellular calcium measurements using fluorescent imaging techniques. The correlation of phosphate chain length to activities at these receptors is discussed.

A series of 2-amino-9-(3-azido-2,3-dideoxy-beta-D-erythro-pentofuranosyl)-6- substituted-9H-purines was synthesized and tested for the ability to protect MT4 cells from the cytopathic effect of HIV-1IIIB. These compounds were prepared by a combination of chemical and enzymatic reactions. Some of the nucleoside analogs with 6-alkoxy, 6-alkylamino, or 6-arylamino substituents were active against HIV-1IIIB. Their IC50 values were in the range of 2-60 microM. In contrast, analogs with 6-thio, 6-alkylthio, 6-methyl, or 6-carbonitrile substituents did not protect cells from the cytopathic effect of HIV infection.

3'-Amino-2',3'-dideoxyribonucleosides of thymine, uracil, and 5-iodouracil (1-3) were synthesized from the corresponding 2'-deoxyribonucleosides via the threo-3'-chloro and the erythro-3'-azido derivatives. Corresponding aminonucleosides of 5-bromouracil, 5-chlorouracil, and 5-fluorouracil (4-6) were synthesized enzymatically with 3'-amino-2',3'-dideoxythymidine as the aminopentosyl donor and thymidine phosphorylase (EC 2.4.2.4) as the catalyst. 3'-Amino-2',3'-dideoxycytidine (7) was synthesized by amination of the 3'-azido precursor of 3'-amino-2',3'-dideoxyuridine. The biological activity of 3'-amino-2',3'-dideoxy-5-fluorouridine (6) was notable among this group of aminonucleosides. It had an ED50 of 10 microM against adenovirus and was not appreciably cytotoxic to mammalian cells in culture. It also had activity against some Gram-positive bacteria but not against a variety of Gram-negative bacteria. The other aminonucleosides (1-5 and 7) lacked or exhibited weak antiviral and antibacterial activities. The only compounds in this group that were appreciably toxic to mammalian cells in culture were the thymidine and deoxycytidine analogues (1 and 7).