Synthesis and enzymatic and inotropic activity of some new 8-substituted and 6,8-disubstituted derivatives of adenosine cyclic 3',5'-monophosphate.

The synthesis of certain new 8-(arythio)- and 8-(alkylthio)-cAMP derivatives and N6-alkyl- and N6-dialkyl-8-(arylthio) and -8-(alkylthio) derivatives of cAMP is reported. On the basis of activation of protein kinase, several N6-alkyl-8-(benzylthio)-cAMP derivatives were selected for evaluation as inotropic agents using cat papillary muscle in vitro. Activity in these studies resulted in the selection of several analogues for in vivo studies in the anesthetized dogs. The best inotropic agent selected on the basis of in vivo studies was N6-butyl-8-(benzylthio)-cAMP (26), which exhibited an increase in blood-flow rate of 85% with no increase in heart rate. A large-scale synthesis of 26 from cAMP is reported via N1-alkylation, followed by a Dimroth rearrangement, reduction, bromination, and nucleophilic displacement via benzyl mercaptan. The N6-alkyl-8-substituted-cAMP derivatives represent a new class of potent inotropic agents. The direct mechanism of action of 26 suggests the possible utility of this cyclic nucleotide to treat clinical myocardial infarction by rapid intravenous infusion.

Synthesis and antiviral acticity of some phosphates of the broad-spectrum antiviral nucleoside, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (ribavirin).

1-beta-D-Ribofuranosyl-1,2,4-triazole-3-carboxamide 5'-phosphate (2) was prepared and converted into the following derivatives: the 5'-phosphoramidate 3, the 5'-diphosphate 4, the 5'-triphosphate 5, and the cyclic 3',5'-phosphate 6. The cyclic 2',3'-phosphate 7 was prepared from the parent nucleoside, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (1), and was opened to the 2'(3')-phosphate 8. These compounds were found to exhibit significant antiviral activity against several viruses in cell culture. Ribavirin 5'-phosphate (2) was shown to be effective when tested against lethal infections in mice caused by influenza A2, influenza B, and murine hepatitis viruses.

Synthesis and enzymic activity of 8-acyl and 8-alkyl derivatives of guanosine 3, 5-cyclic phosphate.

Several new 8-alkyl and 8-acyl derivatives of quanosie 3',5'-cyclic phosphate (cGMP) and inosine 3',5'-cyclic phosphate (cGMP) were prepared by direct alkylation or acylation of the parent cyclic nucleotide via free radicals generated in situ. These compounds have been examined for their ability to stimulate a cGMP-dependent protein kinase, and several of the cGMP derivatives were as active in this regard as cGMP. These compounds proved to be quite ineffective when tested for their ability to activate an adenosine 3',5'-cyclic phosphate (cAMP) dependent protein kinase. In addition, these 8-substituted cGMP derivatives are not substrates for a phosphodiesterase preparation from rabbit kidney, but do show inhibition of the hydrolysis of cAMP by crude phosphodiesterase preparations from rabbit lung and beef heart.

Interaction of "aza" and "deaza" analogs of adenosine cyclic 3', 5'-phosphate with some enzymes of adenosine cyclic 3', 5'-phosphate metabolism: evidence that the lone pair electrons of N-3 are involved in the binding of adenosine cyclic 3', 5'-phosphate to type II adenosine cyclic 3', 5'-phosphate-dependent protein kinase.

Five hetercyclic analogs of adenosine cyclic 3',5'-phosphate (cyclic AMP) were examined for their ability (1) to stimulate type II cyclic AMP-dependent kinases from bovine brain, bovine heart, and rat liver; (2) to serve as substrates for "high Km" (Km for cyclic AMP = 0.13-0.43 mM) cyclic nucleotide phosphodiesterases from bovine heart, rabbit kidney, and rat liver; and (3) to inhibit the hydrolysis of cyclic AMP catalyzed by "low Km" (Km for cAMP = 0.32-1.5 muM) cyclic nucleotide phosphodiesterases from bovine brain, bovine heart, dog heart, rabbit liver, rat brain and rat liver. The analogs all had a purine ring system which had been modified by replacement of a ring carbon with nitrogen or vice versa to yield 2-aza-cAMP (7-amino-4-beta-D-ribofuranosylimidazo [4,5-d] -v-triazine cyclic 3',5'-phosphate); 8-aza-cAMP (7-amino-3-beta-D-ribofuranosyl-v-triazolo-[4,5-d]-pyrimidine cyclic 3',5'-phosphate); 1 deaza-cAMP (7-amino-3-beta-D-ribofuranosylimidazo [4,5-b[pyridine cyclic 3',5'-phosphate); 3-deaza-cAMP (4-amino-1-beta-D-ribofuranosylimidazo[4,5-c]pyridine cyclic 3',5'-phosphate) and 7-deaza-cAMP (7-amino-4-beta-D-ribofuranosylpyrrolo[2,3-d]pyrimidine cyclic 3',5'-phosphate).