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An efficient and highly selective multicomponent synthesis of 4-aminoimidazo[1,2-a][1,3,5]triazines, which are 5-aza-7-deaza-isosteres of adenine, was developed. The reaction of 2-aminoimidazoles, triethyl orthoformate and cyanamide under microwave irradiation proceeded regioselectively to provide a library of novel 5-aza-7-deaza-adenines in good yields and purity. The developed method was demonstrated to be scalable and highly reproducible in three different monomode microwave reactors. A rearrangement was proposed to explain the high selectivity of the reaction.

An efficient and highly selective multicomponent synthesis of 4-aminoimidazo[1,2-a][1,3,5]triazines, which are 5-aza-7-deaza-isosteres of adenine, was developed. The reaction of 2-aminoimidazoles, triethyl orthoformate and cyanamide under microwave irradiation proceeded regioselectively to provide a library of novel 5-aza-7-deaza-adenines in good yields and purity. The developed method was demonstrated to be scalable and highly reproducible in three different monomode microwave reactors. A rearrangement was proposed to explain the high selectivity of the reaction.

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. Exploring the pharmacologically important pyrazolo[1,5-a][1,3,5] triazin-7(6H)-one scaffold for the construction of new bioactive compounds, we developed a synthesis of 4-phenethylthio-2- phenylpyrazolo[1,5-a][1,3,5] triazin-7(6H)-one (4) via S-alkylation of 2-phenyl-4-thioxopyrazolo [1,5-a][1,3,5] triazine-7(6H)-one (3), prepared by the double ring closure of pyrazole and triazine rings upon the treatment of 1-cyanoacetyl-4-benzoylthiosemicarbazide (2) with alkali. The antiproliferative activity of 4 against human lung cancer (A549) and human breast cancer (MDA-MB231) cell lines was investigated. Compound 4 was found to be more active against lung cancer cells t han breast cancer cells.

An efficient and highly selective multicomponent synthesis of 4-aminoimidazo[1,2-a][1,3,5] triazines, which are 5-aza-7-deaza-isosteres of adenine, was developed. The reaction of 2-aminoimidazoles, triethyl orthoformate and cyanamide under microwave irradiation proceeded regioselectively to provide a library of novel 5-aza-7-deaza-adenines in good yields and purity. The developed method was demonstrated to be scalable and highly reproducible i n three different monomode microwave reactors. A rearrangement was proposed to explain the high selectivity of the reaction.

© 2017 The Japan Institute of Heterocyclic Chemistry. 5-Aminotetrazole is a useful building block in organic synthesis, including various multicomponent reactions (MCRs). In MCRs, 5-aminotetrazole usually plays a role of 1,3-binucleophilic reagent, but in some reactions, the only reactive centre is an exocyclic amino group of 5-aminotetrazole. This review systematises MCRs involving 5-aminotetrazole forming a background for further investigations in this area.

© 2017 Elsevier Ltd.An improved microwave-assisted method was developed for the preparation of ethyl 5-aminopyrazole carboxylates from ethyl 2-cyano-3-methylthioacrylates and hydrazine. It was shown that using microwave irradiation significantly reduced the reaction time and improved the process selectivity and yield. The reaction proved to be reproducible in different microwave reactors and on large scale, affording the desired products in high yields and purity. A representative library of 3-arylamino-substituted 5-aminopyrazole-4-carboxylates was successfully prepared to assess the scope of the method.

Novel fluorinated 4-benzylamino-7-phenylpyrazolo[1,5-a]- [1,3,5]triazin-2-amines were prepared using an efficient and practical approach. The chemoselectivity of condensation of pyrazolylguanidine and trichloroacetonitrile was found to be solvent-dependent and, when conducted in toluene, this reaction afforded 7-phenyl-4-trichloromethylpyrazolo[1,5-a]- [1,3,5]triazin-2-amine as the main product. This key intermediate underwent nucleophilic replacement of the trichloromethyl group with fluorinated benzylamines providing a series of the target compounds. Antiproliferative activity of the prepared compounds against Jurkat T cells was explored using MTS assay. Morphological changes observed in cells treated by the most potent compounds of this series, suggested that these compounds induced apoptosis in cells.

A one-pot, three-component, microwave-assisted reaction of polysubstituted 5-aminopyrazoles, triethyl orthoformate, and a series of cyclic secondary amines was developed and successfully employed for the synthesis of novel N-pyrazolylformamidines. Under catalyst-free conditions, the reaction proceeded in a chemo- and regioselective manner, resulting in the formation of unsymmetric formamidines, which were isolated in high yields and purity. Some of the prepared compounds were found to inhibit interleukin-17 secretion in phenotypic in vitro assays.

New fluorinated 7-benzylamino-2-phenyl-1,2,4-triazolo[1,5-a][1,3,5]triazin-5-amines were designed as potential anticancer agents and a practical method for their preparation was developed. The reaction of benzhydrazide with cyanoguanidine followed by intramolecular cyclocondensation resulted in the formation of triazolylguanidine, which upon condensation with trichloroacetonitrile afforded a key intermediate - 2-phenyl-7-trichloromethyl-1,2,4-triazolo[1,5-a][1,3,5]triazin-5-amine. In mild conditions, this intermediate underwent nucleophilic displacement of the trichloromethyl group with a series of fluorinated benzylamines providing the target compounds. Antiproliferative activity of the prepared compounds against the lung and breast cancer cells was explored. Together with anticancer effect, some compounds demonstrated anti-angiogenic properties.

The synthesis of novel 7-amino-substituted pyrazolo[1,5-a][1,3,5]triazine-8-carbonitriles was achieved via a three-component reaction of 3-amino-substituted 5-aminopyrazole-4-carbonitriles, cyanamide and triethyl orthoformate under microwave irradiation. Under catalyst-free conditions, this three-component reaction accommodated a generous diversity of amino substituents making it ideal for the generation of compound libraries for drug discovery processes.

© 2015 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. A method for the preparation of novel pyrimido[1,2-a][1,3,5]triazin-6-one derivatives functionalized in positions 2, 4, and 7 of the ring was developed. Diversity in the derivatization of the pyrimido[1,2-a][1,3,5]triazin-6-one scaffold was successfully achieved by the introduction of substituents into positions 2 and 7 via two complementary approaches for the synthesis of key intermediates viz. pyrimidinylguanidines. Variations in position 4 of the pyrimido[1,2-a][1,3,5]triazine ring were made available by the regioselective introduction of various substituents via the triazine ring closure with corresponding aldehydes. The scope of the method was illustrated by the preparation of a library of 66 pyrimido[1,2-a][1,3,5]triazin-6-ones, which was demonstrated to be a source for new selective anticancer agents. Tautomeric preferences and anticancer properties were also explored for the prepared compounds.

Use of safer solvents satisfies green chemistry practices. From the green chemistry perspective, the best solvent for reactions is no solvent. However, this ideal situation is not always achievable and choice of more eco-friendly solvents becomes critical. This chapter is dedicated to the synthesis of heterocyclic compounds using supercritical carbon dioxide and unconventional eco-friendly solvents with good biodegradability potential, such as polyethylene glycols (PEGs) and some bio-derived solvents (glycerol, ethyl lactate, and gluconic acid aqueous solution). These reaction media have enormous potential for use in medicinal chemistry with many advantages over conventional organic solvents. Supercritical carbon dioxide differs from the conventional solvents by its extremely low gas-like viscosity and great diffusivity. At the same time, supercritical carbon dioxide possesses an excellent profile from the health, safety, and environment perspective. Moreover, being an excellent solvent, supercritical carbon dioxide also acts as a very useful green reagent in a number of important transformations, including heterocyclizations. PEGs are nontoxic and biodegradable polymers with molecular weight ranging from 200 to 20,000 g/mol. This provides a good choice of PEGs for a better reaction outcome. In a number of reactions, PEG, being a solvent, also plays a role of a catalyst promoting the reaction. Bio-derived solvents such as glycerol, ethyl lactate, and gluconic acid possess enormous potential for heterocyclic chemistry, especially in combination with other green chemistry tools like microwave irradiation. Use of these unconventional solvents in the synthesis of heterocyclic compounds of biological importance is exemplified in this chapter.

CONTEXT: Verbascum nigrum L. (Scrophulariaceae) is a perennial plant used in folk medicine for the treatment of kidney diseases due to its presumable diuretic properties. OBJECTIVE: We investigated the diuretic activity and toxicity of extracts from different parts of V. nigrum and identified a group of compounds responsible for the biological effect. MATERIALS AND METHODS: Five ethanol extracts from herb, roots, flowers, leaves and stems as well as five fractions of polar compounds isolated from herb of V. nigrum were orally administrated as a single dose of 50 mg/kg to rats. Urinary excretion and electrolyte content were measured at 3 and 6 h after the treatment. The acute toxicity of the V. nigrum extracts and fractions was evaluated in mice.RESULTS: All extracts, except the one prepared from the roots, showed a significant increase of the urine output within first 3 h after their administration. The extract from stems was the most active, inducing urine output of 14.6 ± 0.8 ml/kg BW versus 5.2 ± 1.4 ml/kg BW of the control. It also demonstrated saluretic activity with a natriuretic index 4.1 and a kaliuretic index 3.8. The diuretic activity was correlated with the flavonoid content in the plant organs. Flavonoid fractions demonstrated significant activity; the higher content of flavonoids (expressed as hesperidin) translated into more pronounced diuretic (35.9 ± 2.1 ml/kg BW) and saluretic effects (natriuretic index 4.5 and kaliuretic index 5.4). CONCLUSION: The diuretic activity of traditionally used V. nigrum was validated experimentally. The pharmacological effect was attributed to flavonoids, which accumulated in aerial parts of the plant, mainly in stems.

In our drug discovery program, a series of 2-thioxo-pyrazolo[1,5-a][1,3,5] triazin-4-ones were designed, synthesized and evaluated for their TP inhibitory potential. All the synthesized analogues conferred a varying degree of TP inhibitory activity, comparable or better than positive control, 7-deazaxanthine (7-DX, 2) (IC50 value = 42.63 µM). A systematic approach to the lead optimization identified compounds 3c and 4a as the most promising TP inhibitors, exhibiting mixed mode of enzyme inhibition. Moreover, selected compounds demonstrated the ability to attenuate the expression of the angiogenic markers (viz. MMP-9 and VEGF) in MDA-MB-231 cells at sublethal concentrations. In addition, molecular docking studies revealed the plausible binding orientation of these inhibitors towards TP, which was in accordance with the experimental results. Taken as a whole, these compounds would constitute a new direction for the design of novel TP inhibitors with promising antiangiogenic properties. © 2014 Elsevier Masson SAS. All rights reserved.

In our lead finding program, a series of 5-thioxo-[1,2,4]triazolo[1,5-a][1, 3,5]triazin-7-ones and their 5-thio-alkyl derivatives were designed and synthesized which contained different substituents at ortho-position of 2-phenyl ring attached to the fused ring structure. The preliminary pharmacological evaluation demonstrated that the synthesized compounds exhibited a varying degree of inhibitory activity towards thymidine phosphorylase (TP), comparable to reference compound, 7-Deazaxanthine (7-DX, 2) (IC50 value = 42.63 lM). The study also inferred that the ortho-substituted group at the phenyl ring and 5-thio-alkyl moiety imparted steric hindrance effects in the binding site of the enzyme, leading to a reduced inhibitory response. In addition, compound 3a was identified as a mixed-type inhibitor of TP. Moreover, computational docking study was performed to illustrate the important structural information on the plausible ligand-enzyme binding interactions. © 2013 Elsevier Inc. All rights reserved.

We describe here the design, synthesis and evaluation of in vivo local anaesthetic and antiarrhythmic activities of a series of N-alkylproline anilides. Most of the compounds demonstrated surface anaesthetic activity higher than that of lidocaine, ropivacaine and bupivacaine. We established that the local anaesthetic activity was sensitive to structural variations in the substitution pattern at the aromatic ring and the type of alkyl group at the proline nitrogen atom. Some of the prepared N-alkylproline anilides possessed significant antiarrhythmic activity with higher therapeutic indexes than the reference drugs.

A new, efficient, catalyst-free, one-pot, three-component method for the synthesis of 2-amino-substituted 7-amino-1,2,4-triazolo[1,5-a][1,3,5]triazines using 3,5-diamino-1,2,4-triazoles, cyanamide, and triethyl orthoformate is developed. The reaction proceeds smoothly under microwave-assisted heating. Advantages of the method include using easily available reagents, short reaction times, and operational simplicity.

The amino substituted triazine ring was annelated to aminoazoles using a new effective synthetic procedure. The method of preparation involved initial formation of azolylformamidines in the reaction of aminoazoles with N,N-dimethylformamide dimethyl acetal followed by the triazine ring closure with cyanamide affording therefore fused aminotriazines.

Thirty-three 1,2,4-triazolo[1,5-a][1,3,5]triazin-5,7-dione and its 5-thioxo analogues were designed and synthesized which contained different substituents at meta- and/or para-positions of 2-phenyl or 2-benzyl ring attached to the fused ring structure. The preliminary pharmacological evaluation demonstrated that the 5-thioxo analogues of 1,2,4-triazolo[1,5-a][1,3,5]triazine exhibited a varying degree of inhibitory activity towards thymidine phosphorylase, comparable or better than reference compound, 7-Deazaxanthine (7-DX, 2) (IC 50 value = 42.63 µM). Moreover, compounds 5q and 6i displayed a mixed-type of inhibitory mechanism in the presence of variable concentrations of thymidine (dThd). In addition, selected compounds were found to have a noticeable inhibitory effect on the expression of angiogenesis markers, including VEGF and MMP-9 in MDA-MB-231 breast cancer cells. © 2013 Elsevier Masson SAS. All rights reserved.

5-Chlorouracil-linked-pyrazolo[1,5-a][1,3,5]triazines were designed as new thymidine phosphorylase inhibitors based on the fragment based drug design approach. Multiple-step convergent synthetic schemes were devised to generate the target compounds. The intermediate 5-chloro-6-chloromethyluracil was synthesized by a 4-step reaction. A series of the second bicyclic intermediates, namely pyrazolo[1,5-a][1,3,5]triazin-2-thioxo-4-one, was obtained from various substituted 3-aminopyrazoles. These two intermediates were coupled finally in the presence of sodium ethoxide and methanol to yield the desirable target compounds. The methylthio coupling spacer was found to be suitable in enabling the interaction of the two fragments at the active site and allosteric site of the enzyme. The best coupled compound (9q) inhibited the thymidine phosphorylase with an IC50 value as low as 0.36 ± 0.1 µM. In addition, 9q demonstrated a mixed-type of enzyme inhibition kinetics, thus suggesting that it might indeed potentially bind at two different sites on the enzyme. © Georg Thieme Verlag KG Stuttgart New York ISSN 0935-8943.

A novel multicomponent strategy for the efficient synthesis of 5-aza-adenines was developed. 5-Azaadenines were prepared in a one-pot fashion from 5-amino-1,2,4-triazoles, cyanamide and triethylorthoformate under microwave irradiation. The operational simplicity, efficiency and accessibility of thismethod make it highly attractive for the generation of bioactive compound libraries

In our lead finding program, a series of 1,2,4-triazolo[1,5-a][1,3,5]triazine derivatives were synthesized, and their in vitro thymidine phosphorylase inhibitory potential was explored. Among the different derivatives, compounds having keto group (C = O) at C7 and thioketo group (C = S) at C5 positions showed varying degrees of TP inhibitory activity comparable with positive control, 7-deazaxanthine (7-DX, 2) (IC50 value = 42.63 µm). Enzyme inhibition kinetics study suggested that compound IVn behaved as a mixed-type inhibitor of the enzyme with respect to thymidine (dThd) as a variable substrate. Compound IVn was also found to inhibit PMA-induced MMP-9 expression in MDA-MB-231 cells at sublethal concentrations. Computational docking study was performed to illustrate the enzyme inhibition kinetics and to explore the ligand-enzyme interactions. © 2013 John Wiley & Sons A/S.

Based on structural similarities with the reference compounds, a series of 1,3,5-triazin-2,4-dione and their fused analogues was designed, synthesized and their in vitro thymidine phosphorylase inhibitory potential was evaluated. The monocyclic analogues were found to be inactive. Among the different fused derivatives synthesized, compounds having keto group (C=O) at C7/C4 and thioketo group (C=S) at C5/C2 position showed TP inhibitory activity comparable to positive control, 7-deazaxanthine (7-DX) (IC50 value = 42.63 µM). Molecular docking of the target compounds into the enzyme thymidine phosphorylase was performed to illustrate the important structural information on the plausible ligand-enzyme-binding interactions. © 2013 Springer Science+Business Media New York.

The triazine ring bearing a trichloromethyl group was annelated to various aminoazoles using a new effective synthetic procedure. The method of preparation involved initial formation of trichloroacetamidines in the reaction of aminoazoles with trichloroacetonitrile followed by the triazine ring closure with triethyl orthoformate affording therefore the titled compounds.

A novel thermal rearrangement, involving pyrimidine ring opening and subsequent ring closure leading to recyclization of the system, was identified in the reaction of (6-oxo-1,6- dihydropyrimidin-2-yl)guanidines 3 (where NR1R2 = NH2, NH alkyl, NH aralkyl, NHCH2Ph(R)) with triethyl orthoacetate, affording 4-substituted-2-methyl-6H-pyrimido[1,2-a][1,3,5]triazin-6- ones 6 and their ring opened products. However, no such rearrangement was observed with (6- oxo-1,6-dihydropyrimidin-2-yl)guanidines 3 bearing a tertiary amino or anilino substituent (i.e. where NR1R2 = N(CH3)2, indoline, morpholino, NHAr). As expected, 2-substituted-4-methyl- 6H-pyrimido[1,2-a][1,3,5]triazin-6-ones 4 were obtained as the final products. Experimental 2 structural determination and theoretical studies were carried out to get an understanding of the observed thermal rearrangement. In addition, an attempt to obtain similar pyrimido[1,2-a][1,3,5]triazin-6-ones using N,N-dimethylacetamide dimethyl acetal (DMA-DMA) as one carbon inserting synthon had furnished triazine ring annulated product 14 bearing N,N-dimethyl enamino substituent at position 4 as a result of further reaction with a second molecule of DMA-DMA.