Dimroth rearrangement-based synthesis of novel derivatives of [1,3]selenazolo[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine as a new class of selenium-containing heterocyclic architecture

Design and synthesis of novel main protease inhibitors of COVID-19: quinoxalino[2,1-b]quinazolin-12-ones

The COVID-19 pandemic represents a substantial global challenge, being a significant cause of mortality in numerous countries. Thus, it is imperative to conduct research to develop effective therapies to combat COVID-19. The primary aim of this study is to employ a two-step tandem reaction involving 2,3-dichloroquinoxaline and 2-amino-N-substituted benzamides in alkaline media/DMF at an elevated temperature to design and synthesize a series of polycyclic derivatives endowed with quinoxalino[2,1-b]quinazolin-12-one framework. Following synthesis, the newly synthesized heterocycles were evaluated for their potential as inhibitors of the main protease of SARS-CoV-2 by means of molecular docking and dynamic simulation techniques. The in silico investigation demonstrated that all tested compounds effectively establish stable binding interactions, primarily through multiple hydrogen bonding and hydrophobic interactions, at the active site of the enzyme. These findings offer crucial structural insights that can be employed in future endeavors toward designing potent inhibitors targeting the main protease (Mpro). Among the investigated compounds, the p-tolylamino-substituted quinoxalino[2,1-b]quinazolinone derivative exhibited the most promise as an inhibitor of the main protease in COVID-19. Consequently, it warrants further investigation both in vitro and in vivo to identify it as a prospective candidate for anti-SARS-CoV-2 drug development.

Domino protocol for the synthesis of diversely functionalized derivatives of a novel fused pentacyclic antioxidant/anticancer fluorescent scaffold: Pyrazolo[5'',1'':2',3']pyrimido[4',5':5,6][1,4]thiazino[2,3-b]quinoxaline

Rising to the challenge of formidable multi-step reaction needed for the synthesis of polycyclic compounds, an efficient one-pot two-step procedure for the synthesis of densely functionalized novel pyrazolo[5″,1'':2',3']pyrimido[4',5':5,6] [1,4]thiazino[2,3-b]quinoxalines from synthetically accessible starting materials 6-bromo-7-chloro-3-cyano-2-(ethylthio)-5-methylpyrazolo[1,5-a]pyrimidine, 3-aminoquinoxaline-2-thiol and some readily accessible alkyl halides was established. The domino reaction pathway involves cyclocondensation/N-alkylation sequence in K₂CO₃/N,N-dimethyl formamide under heating condition. DPPH free radical scavenging activity of all synthesized pyrazolo[5″,1'':2',3']pyrimido[4',5':5,6][1,4]thiazino[2,3-b]quinoxalines was evaluated to determine their antioxidant potentials. IC₅₀ values were recorded in the range of 29-71 μM. N-benzyl substituted derivative represented the most effective antioxidant activity as well as antiproliferative activity against MCF-7 cells. Moreover, fluorescence in solution for these compounds exhibited strong red emission in the visible region (λ_flu. = 536-558 nm) with good to excellent quantum yields (61-95%). Due to their interesting fluorescence properties, these novel pentacyclic fluorophores can be used as fluorescent markers and probes for studies in biochemistry and pharmacology.

Pyrido[1,2-e]purine: Design and Synthesis of Appropriate Inhibitory Candidates against the Main Protease of COVID-19

A series of tricyclic and polycyclic pyrido[1,2-e]purine derivatives were designed and synthesized via a two-step, one-pot reaction of 2,4-dichloro-5-amino-6-methylpyrimidine with pyridine under reflux conditions. Various derivatives of pyrido[1,2-e]purine were also synthesized by substituting the chlorine atom with secondary amines. After careful physiochemical and pharmacokinetic predictions, the inhibitory effects of the synthesized compounds against the main protease of SARS-CoV-2 have been evaluated by molecular docking and molecular dynamics approaches. The in silico results revealed that among all of the studied compounds, the morpholine/piperidine-substituted pyrido[1,2-e]purine derivatives are the best candidates as effective inhibitors of SARS-CoV-2.

A Dimroth rearrangement approach for the synthesis of selenopheno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidines with cytotoxic activity on breast cancer cells

New selenopheno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives have been synthesized via Dimroth rearrangement by cyclocondensation of 7-cyano-4-hydrazinyl-6-(pyrrolidin-1-yl)selenopheno[3,2-d]pyrimidine with electrophilic carbons of either orthoesters in acetic acid or carbon disulfide in pyridine followed by S-alkylation. All the newly synthesized products have been structurally elucidated. The in vitro anticancer screening of the tricyclic Se-containing heterocycles was accomplished against human breast carcinoma MCF-7 cancerous cell line and L929 cells. Anticancer results revealed that the S-hexyl-substituted compound with an IC₅₀ value of 158.9 µM in 72 h was foremost among others in cytotoxic potency. In the following order, S-pentyl and S-ethyl-substituted derivatives with IC₅₀ values of 216.1 and 396.5 µM were second and third efficient compounds as in anticancer activity, respectively. The inhibitory effects of the mentioned compounds were less on the growth of L929 cells.