1.Synthesis of [1,2,4]triazolo[1,5-a]pyrazines as adenosine A2A receptor antagonists.
Dowling JE1, Vessels JT, Haque S, Chang HX, van Vloten K, Kumaravel G, Engber T, Jin X, Phadke D, Wang J, Ayyub E, Petter RC. Bioorg Med Chem Lett. 2005 Nov 1;15(21):4809-13.
Potent and selective antagonists of the adenosine A2A receptor often contain a nitrogen-rich fused-ring heterocyclic core. Replacement of the core with an isomeric ring system has previously been shown to improve target affinity, selectivity, and in vivo activity. This paper describes the preparation, by a novel route, of A2A receptor antagonists containing the [1,2,4]triazolo[1,5-a]pyrazine nucleus, which is isomeric with the [1,2,4]triazolo[1,5-c]pyrimidine core of a series of known A2A antagonists with in vivo activity in animal models of Parkinson's disease.
2.4-Pyridylnitrene and 2-pyrazinylcarbene.
Wentrup C1, Reisinger A, Kvaskoff D. Beilstein J Org Chem. 2013 Apr 17;9:754-60. doi: 10.3762/bjoc.9.85. Print 2013.
Both flash vacuum thermolysis (FVT) and matrix photolysis generate 2-diazomethylpyrazine (22) from 1,2,3-triazolo[1,5-a]pyrazine (24). FVT of 4-azidopyridine (18) as well as of 24 or 2-(5-tetrazolyl)pyrazine (23) affords the products expected from the nitrene, i.e., 4,4'-azopyridine and 2- and 3-cyanopyrroles. Matrix photolyses of both 18 and 24 result in ring expansion of 4-pyridylnitrene/2-pyrazinylcarbene to 1,5-diazacyclohepta-1,2,4,6-tetraene (20). Further photolysis causes ring opening to the ketenimine 27.
3.Design, synthesis, and structure-activity relationship studies of novel fused heterocycles-linked triazoles with good activity and water solubility.
Cao X1, Sun Z, Cao Y, Wang R, Cai T, Chu W, Hu W, Yang Y. J Med Chem. 2014 May 8;57(9):3687-706. doi: 10.1021/jm4016284. Epub 2014 Mar 7.
Triazoles with fused-heterocycle nuclei were designed and evaluated for their in vitro activity on the basis of the binding mode of albaconazole using molecular docking, along with SAR of antifungal triazoles. Tetrahydro-[1,2,4]triazolo[1,5-a]pyrazine and tetrahydro-thiazolo[5,4-c]pyridine nuclei were preferable to the other four fused-heterocycle nuclei investigated. Potent in vitro activity, broad spectrum and better water solubility were attained when triazoles containing nitrogen aromatic heterocycles were attached to these two nuclei. The most potent compounds 27aa and 45x, with low hERG inhibition and hepatocyte toxicity, both exhibited excellent activity against Candida, Cryptococcus, and Aspergillus spp., as well as selected fluconazole-resistant strains. A high water-soluble compound 58 (the disulfate salt of 45x) displayed unsatisfactory in vivo activity because of its poor PK profiles. Mice infected with C.alb. SC5314 and C.alb.
4.Synthesis of alkyne derivatives of a novel triazolopyrazine as A(2A) adenosine receptor antagonists.
Yao G1, Haque S, Sha L, Kumaravel G, Wang J, Engber TM, Whalley ET, Conlon PR, Chang H, Kiesman WF, Petter RC. Bioorg Med Chem Lett. 2005 Feb 1;15(3):511-5.
A novel [1,2,4]triazolo[1,5-a]pyrazine core was synthesized and coupled with terminal acetylenes. The structure-activity relationship of the alkynes from this novel template was studied for their in vitro and in vivo adenosine A(2A) receptor antagonism. Selected compounds from this series were shown to have potent in vitro and in vivo activities against adenosine A(2A) receptor. Compound 12, in particular, was found to be orally active at 3mg/kg in both a mouse catalepsy model and a 6-hydroxydopamine-lesioned rat model.