Design, synthesis, biological evaluation and molecular docking of cyclic biguanidine compounds as cholinesterase inhibitors

A series of cyclic biguanidine derivatives (E01-E16) was designed, synthesized, characterized by FTIR, NMR, elemental analysis and evaluated as cholinesterase [acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)] inhibitory effects for the treatment of Alzheimer's disease (AD). The cyclic biguanidine derivatives (E01-E16) were obtained as hydrochloride salt from one-pot reaction of 2-cyanoguanidine, p-substitute aniline derivatives and cyclohexanone/4-ethylcyclohexanone in the acidic medium. The crystal structures of compounds E13 and E16 were determined by XRD studies. The in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory assessment of the compounds revealed that compounds showed considerable inhibitory activity. The substitute groups on the phenyl rings have an impact on the inhibitory activity of the compounds. Compound E08, containing an ester group on the phenyl ring, showed the highest inhibitory activity against BuChE (IC50: 97.97 ± 0.13 µM) compared to other compounds. According to the docking result, compound E08 exhibited higher binding affinity (-10.17 kcal/mol) against BuChE than the standard drug tacrine (-7.02 kcal/mol). Compound E08 was orientated towards the active site of the enzyme BuChE.Communicated by Ramaswamy H. Sarma.

An Efficient Synthesis of Novel 4-Aryl-2-thioxo-3,4-dihydro-1H-pyrimido[1,2-a][1,3,5]triazin-6(2H)-ones and Their Antibacterial Activity

New substituted 4-aryl-8-methyl-2-thioxo-1,2,3,4-tetrahydro-6H-pyrimido[1,2-a][1,3,5]triazin-6-one 8a–b and ethyl 4-aryl-6-oxo-2-thioxo-1,3,4,6-tetrahydro-2H-pyrimido[1,2-a][1,3,5]triazine-7-carboxylate 8c–e were synthesized by the reaction of the corresponding 4-oxopyrimidin-2-ylthioureas with arylaldehydes. The formation of only one regioisomer was proven using complex spectral data and its structure was characterized. It was found that the interaction of 6-amino-4-phenyl-3,4-dihydro-1,3,5-triazine-2(1H)-thione with ethyl acetoacetate and diethyl ethoxymethylenemalonate leads to the formation of the same regioisomer. That is, changing the sequence of stages in this cascade process does not affect the structure of the final reaction product. All synthesized compounds exhibit antibacterial activity against E. coli and S. aureus cultures at a concentration (MIC) of 256 µg/mL.

Applications of alkyl orthoesters as valuable substrates in organic transformations, focusing on reaction media

In this review we focus on applications of alkyl orthoesters as valuable and efficient substrates to perform various classes of two-component and multi-component organic reactions. The article has classified them according to two aspects, which are: (i) a focus on the reaction medium (solvent-free conditions, aqueous media, and organic solvents); and (ii) an examination of product structures. Reaction accomplishment under solvent-free conditions is an eco-friendly process with the absence of volatile toxic solvents, which puts it in line with green chemistry goals. Water is an interesting choice in organic transformations due to its inexpensiveness and safety. The authors hope their assessment will help chemists to attain new approaches for utilizing alkyl orthoesters in various organic synthetic methods. The review covers the corresponding literature up to the beginning of 2020.

Pyrimidotriazine derivatives as selective inhibitors of HBV capsid assembly

Chronic hepatitis B virus (HBV) infection is currently treated with nucleoside/nucleotides analogs. They are potent inhibitors of HBV DNA polymerase, which also functions as reverse transcriptase. Although nucleoside/nucleotide analogs efficiently suppress HBV replication in liver cells, they cannot eradicate HBV DNA from liver cells and cure the disease. Therefore, it is still mandatory to identify and develop effective inhibitors that target a step other than reverse transcription in the viral replication cycle. HBV capsid assembly is a critical step for viral replication and an attractive target for inhibition of HBV replication. We conducted in silico screening of compounds expected to bind to the HBV capsid dimer-dimer interaction site. The selected compounds were further examined for their anti-HBV activity in vitro. Among the test compounds, novel pyrimidotriazine derivatives were found to be selective inhibitors of HBV replication in HepG2.2.15.7 cells. Among the compounds, 2-[(2,3-dichlorophenyl)amino]-4-(4-tert-butylphenyl)-8-methyl-4H,9H-pyrimido[1,2-a][1,3,5]triazin-6-one was the most active against HBV replication. Studies on its mechanism of action revealed that the compound interfered with HBV capsid assembly determined by a cell-free capsid assembly system. Thus, the pyrimidotriazine derivatives are considered to be potential leads for novel HBV capsid assembly inhibitors.

An efficient synthesis of 2,4,7-trisubstituted pyrimido[1,2-a][1,3,5]triazin-6-ones

A practical synthesis of 3,4-dihydro pyrimido[1,2-a][1,3,5]triazin-6-ones, experimental and theoretical assessment of their tautomeric preferences and biological activity results are presented.