Synthesis of new Derivatives of Pyrimido[5,4-e][1,2,4]triazolo[3,4-b] [1,3,4]Thiadiazine and Their Enzyme Inhibitory Activity Assessment on Soybean 15-lipoxygenase

Synthesis and characterisation of new 3-methyl-6-[1-(pyrimidin-4-yl)ethyl]-5H-pyrimido[5,4-e][1,2,4]triazolo[3,4-b][1,3,4]thiadiazine derivatives

A new series of 3-methyl-6-[1-(pyrimidin-4-yl)ethyl]-5 H-pyrimido[5,4- e][1,2,4]triazolo[3,4- b][1,3,4]thiadiazine derivatives was synthesised through the condensation reaction of 5-bromo-4-[1-(5-bromo-2,6-dichloropyrimidin-4-yl)ethyl]-2-chloro-6-methylpyrimidine and 4-amino-5-methyl-4 H-1,2,4-triazole-3-thiol.

Synthesis and Density Functional Theory Study of [1,2,3]Triazolo[4,5-d][1,2,4] Triazolo[4,3-a]Pyrimidine Derivatives: A Novel Heterocyclic System

Several 3H-[1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives of a novel ring system have been synthesised. The initial substitution of the 4-Cl function of 2,4-dichloro-6-methylpyrimidin-5-amine with benzylamine followed by treatment with sodium nitrite generated 3-benzyl-5-chloro-7-methyl-3H-[1,2,3]triazolo[4,5-d]pyrimidine. Nucleophilic substitution of the 5-Cl moiety of the latter compound with hydrazine hydrate and subsequent treatment with carbon disulfide in boiling pyridine gave, quantitatively, the corresponding [1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives. Density functional theory (DFT) studies were also performed to reveal regioselectivity of the ring closure via Gauge-Independent Atomic Orbital (GIAO) 1H NMR calculations. The WP04 method was used as the DFT code to yield accurate chemical shift values. Theoretical results correlated well with the expected regioisomer and aided assignment of the final structure.

Synthesis of Thiazolo[5,4-d][1,2,4]Triazolo[4,3-a]Pyrimidines as a New Class of Heterocyclic Compounds

A new series of 2-aminothia zolo[5,4- d]pyrimidines has been synthesised by treating various amines with the new intermediate, 2,5-dichloro-7-methylthiazolo[5,4- d]pyrimidine. Sequential treatment of the amino derivatives with hydrazine hydrate and triethyl orthoesters gave thiazolo[5,4- d][1,2,4]triazolo[4,3- a]pyrimidines as derivatives of a novel heterocyclic system.

Synthesis of New Derivatives of Pyridazino[6,1-c]Pyrimido[5,4-e][1,2,4]Triazine; a Novel Heterocyclic System

Several derivatives of the novel pyridazino[6,1-c]pyrimido[5,4-e][1,2,4]triazine ring system have been synthesised through heterocyclisation of 5-bromo-2,4-dichloro-6-methylpyrimidine with 3-chloro-6-hydrazinylpyridazine followed by treatment with secondary amines in boiling ethanol.

Synthesis of new derivatives of 10H-benzo[b]pyridazino[3,4-e][1,4]thiazines

New 10H-benzo[b]pyridazino[3,4-e][1,4]thiazines were prepared and evaluated for inhibitory activity against soybean 15-lipoxygenase enzyme. These compounds were synthesized by the sequential treatment of 4-bromo-3,6-dichloropyridazine with 2-aminothiophenol and a secondary amine with the subsequent heterocyclization in the presence of sodium amide.

Synthesis of [1,2,4]Triazolo[3,4-b]Pteridines as a Novel Class of Heterocyclic Compounds

A series of pteridine derivatives have been synthesised through intramolecular cyclisation of 2,4-dichloro-6-methyl-5-nitro pyrimidine with various esters of amino acids. The subsequently reaction of pteridines with hydrazine hydrate and then with triethylorthoesters obtained quantitatively the desired [1,2,4]triazolo[3,4-b]pteridine derivatives as a novel heterocyclic system.

An Alternative Approach to the Synthesis of New Pyrimido[5′,4′:5,6][1,4] Thiazino[2,3-B]Quinoxaline Derivatives

An alternative approach to the synthesis of a series of new pyrimido[5′,4′:5,6][1,4]thiazino[2,3-b]quinoxaline derivatives is described. Reaction of 5-bromo-2,4-dichloro-6-methylpyrimidine and 3-aminoquinoxaline-2-thiol leads to the key intermediate 3-[(5-bromo-2-chloro-6-methylpyrimidin-4-yl)thio]quinoxalin-2-amine. This intermediate can be transformed into the title ring systems by subsequent treatment either with secondary amines followed by intramolecular cyclisation or initial intramolecular cyclisation with subsequent reaction with secondary amines.

Synthesis of [1,2,4]Triazolo[4″,3″:1′,6′]Pyrimido[4′,5′:3,4]Pyridazino[1,6-D] [1,2,4]Triazine; A Novel Tetracyclic System

The condensation reaction of 6-acetyl-3-amino-5-aryl-2-phenyl-2,5-dihydropyridazine-4-carbonitrile with triethyl orthoformate and then with hydrazine hydrate to obtain the new fused bicyclic 4-aryl-5-hydrazinyl-3-(1-hydrazonoethyl)-1-phenyl-1,4-dihydropyrimido[4,5-c]pyridazines via the Dimroth rearrangement is reported. Further cyclisation was achieved by the treatment of latter compounds with triethyl orthoformate to afford several derivatives of a novel tetracyclic fused system [1,2,4] triazolo[4″,3″:1′,6′]pyrimido[4′,5′:3,4]pyridazino[1,6-d][1,2,4]triazine.

Synthesis and evaluation of a new series of 3,5-bis((5-bromo-6-methyl-2-t-aminopyrimidin-4-yl)thio)-4H-1,2,4-triazol-4-amines and their cyclized products 'pyrimidinylthio pyrimidotriazolothiadiazines' as 15- lipo-oxygenase inhibitors

A series of new 3,5-bis((5-bromo-6-methyl-2-t-aminopyrimidin-4-yl)thio)-4H-1,2,4-triazol-4-amines and their cyclized products 'pyrimidinylthio pyrimidotriazolothiadiazines' were designed, synthesized, and evaluated as potential inhibitors of 15-lipo-oxygenase (15-LO). Their syntheses started by initial condensation of 2:1 equivalents of pyrimidine with triazole and subsequent nucleophilic displacement of the chlorine atoms with secondary amines and finally cyclocondensation in the presence of NaNH2. The compounds 4d and 4f showed the best IC50 of 15-LO inhibition (IC50 = 9 and 12 μm, respectively). Compounds 4a-g were docked into 15-LO. We suggest that the hydrogen bonds in quaternary nitrogen of piperazine ring of compounds 4d and 4f appear to play major role in lipo-oxygenase inhibition by this set of synthesized analogs and hydrophobic nature of this protein's binding site should be considered in ongoing investigations.

Pyrimido[5,4-e]tetrazolo[5,1-b][1,3,4]thiadiazines as a new heterocyclic system

Six novel 2-substituted pyrimido[5,4- e]tetrazolo[5,1- b][1,3,4]thiadiazines were prepared via a multistep synthetic sequence beginning with 5-bromo-2,4-dichloro-6-methylpyrimidine.