A DFT investigation of structure and spectroscopic properties of pyrazolo[4,3-e][1,2,4]triazine natural products

Pyrazolotriazines: Biological activities, synthetic strategies and recent developments

Heterocyclic compounds create an important class of molecules that demonstrates various chemical spaces for the definition of effective medicines. Many N-heterocycles display numerous biological activities. Among condensed heterocycles, pyrazolotriazine derivatives have received the attention of researchers owing to the extensive spectrum of biological activities. The reactivity of identified compounds was similar to the free azoles and triazines. The pyrazolotriazine scaffold exhibited antiasthma, antiinflammatory, anticancer, antithrombogenic activity and showed activity for major depression and pathological anxiety. Pyrazolotriazine derivatives also exhibited antibacterial, anticancer, antimetabolites, antidiabetic, antiamoebic, anticonvulsant, antiproliferative activity, human carbonic anhydrase inhibition, cyclin-dependent kinase 2 inhibition, tyrosinase and urease inhibition, MAO-B inhibition, TTK inhibition, thymidine phosphorylase inhibition, tubulin polymerization inhibition, protoporphyrinogen oxidase inhibition, GABA_A agonistic activity, hCRF1 receptor antagonistic activity, and CGRP receptor antagonistic activity. This paper structurally categorized various pyrazolotriazines to isomeric classes into six groups that containing pyrazolo [1,5-d] [1,2,4] triazine, pyrazolo [5,1-c] [1,2,4] triazine, pyrazolo [3,4-e] [1,2,4] triazine, pyrazolo [4,3-e] [1,2,4] triazines, pyrazolo [1,5-a] [1,3,5] triazine, and pyrazolo [3,4-d] [1,2,3] triazine and expressed biological activity, the synthetic procedures for each class of pyrazolotriazines, structure-activity relationship and their mechanism of action. Generally, this review summarily indicated the past and present studies about the discovery of new lead compounds with good biological activity.

Natural Products with Heteroatom-Rich Ring Systems

This review focuses on all known natural products that contain a "heteroatom-rich" ring system, specifically a five-, six- or seven-membered ring that contains three or more heteroatoms. The isolation and biological activity of these natural products is discussed, along with the biosynthetic processes that Nature employs to assemble these rare heterocyclic frameworks.

A DFT investigation of structure, spectroscopic properties and tautomerism of the anticonvulsant drug Lyrica

The Lyrica (Pregabalin) is a novel anticonvulsant and neuropathic pain drug, which could exist as four possible conformers. Herein, employing density functional theory (DFT), and handling the solvent effects with the PCM model, the structural parameters, energetic behavior, natural bond orbital analysis (NBO), as well as tautomerism mechanization of the Lyrica are investigated. The L1 (-OH form) is the most stable conformer of the Lyrica, which can be tautomerized to the L5 (-NH form) tautomer. The tautomerism reaction includes an intramolecular-proton transfer, which affects considerably the structural parameters and atomic charges of the L1. The DFT-computed NMR chemical shifts and IR vibrational frequencies are good in agreement with the experimental values, confirming suitability of the optimized geometry for the Lyrica.

Synthesis and kinase inhibitory activity of new sulfonamide derivatives of pyrazolo[4,3-e][1,2,4]triazines

A new series of sulfonamide derivatives of pyrazolo[4,3-e][1,2,4]triazine has been synthesized and characterized. Their anticancer activity was tested in vitro against multiple human cancer cell lines and were found to have dose-dependent antiproliferative effects. Furthermore, some of the new compounds inhibited the Abl protein kinase with low micromolar IC50 values and exhibited selective activity against the Bcr-Abl positive K562 and BV173 cell lines, providing starting points for the further development of this new kinase inhibitor scaffold.

Natural products containing a nitrogen-nitrogen bond

As of early 2013, over 200 natural products are known to contain a nitrogen-nitrogen (N-N) bond. This report categorizes these compounds by structural class and details their isolation and biological activity.

Molecular structural, IR and NMR spectroscopic studies on the four isomers of thiotriazinone by DFT and HF calculations

One of the isomers of thiotriazinone, 6-hydroxy-2-methyl-3-thioxo-2H-1,2,4-triazin-5-one, was characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2(1)/c with a=9.5837(19)Å, b=5.7006(11)Å, c=15.065(4)Å, α=90°, β=128.540(19)° and γ=90°. The molecular geometries and vibrational frequencies of the four isomers of thiotriazinone in the ground state have been calculated using the density functional theory (DFT) and Hartree-Fock (HF) methods with 6-311++G(d,p) basis set, and compared with the experimental data. Gauge-including atomic orbital (GIAO) (13)C and (1)H NMR chemical shift values were calculated by DFT/6-311++G(2d,2p) and HF/6-311++G(2d,2p) methods, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters. The theoretical IR spectra and (13)C and (1)H NMR chemical shift values also show good agreement with experimental data. In addition, frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) analysis of the four isomers were investigated using theoretical calculations.