The first outbreak in Wuhan, China, in December 2019 was reported about severe acute coronaviral syndrome 2 (SARS-CoV-2). The global coronavirus disease 2019 (COVID-19) pandemic in 2020 resulted in an extremely high potential for dissemination. No drugs are validated in large-scale studies for significant effectiveness in the clinical treatment of COVID-19 patients, despite the worsening trends of COVID-19. This study aims to design a simple and efficient cyclo-condensation reaction of 6-aminouracil derivatives 2a–e and isatin derivatives 1a–c to synthesize spiro-oxindoles 3a–d, 4a–e, and 5a–e. All compounds were tested in vitro against the SARS-CoV-2. Four spiro[indoline-3,5′-pyrido[2,3-d:6,5-d’]dipyrimidine derivatives 3a, 4b, 4d, and 4e showed high activities against the SARS-CoV-2 in plaque reduction assay and were subjected to further RNA-dependent-RNA-polymerase (RdRp) and spike glycoprotein inhibition assay investigations. The four compounds exhibited potent inhibitory activity ranging from 40.23 ± 0.09 to 44.90 ± 0.08 nM and 40.27 ± 0.17 to 44.83 ± 0.16 nM, respectively, when compared with chloroquine as a reference standard, which showed 45 ± 0.02 and 45 ± 0.06 nM against RdRp and spike glycoprotein, respectively. The computational study involving the docking studies of the binding mode inside two proteins ((RdRp) (PDB: 6m71), and (SGp) (PDB: 6VXX)) and geometrical optimization used to generate some molecular parameters were performed for the most active hybrids.

Novel xanthine and imidazolone derivatives were synthesized based on oxazolone derivatives 2a-c as a key intermediate. The corresponding xanthine 3-5 and imidazolone derivatives 6-13 were obtained via reaction of oxazolone derivative 2a-c with 5,6-diaminouracils 1a-e under various conditions. Xanthine compounds 3-5 were obtained by cyclocondensation of 5,6-diaminouracils 1a-c with different oxazolones in glacial acetic acid. Moreover, 5,6-diaminouracils 1a-e were reacted with oxazolones 2a-c in presence of drops of acetic acid under fused condition yielding the imidazolone derivatives 6-13. Furthermore, Schiff base of compounds 14-16 were obtained by condensing 5,6-diaminouracils 1a,b,e with 4-dimethylaminobenzaldehyde in acetic acid. The structural identity of the resulting compounds was resolved by IR, ¹H-, ¹³C-NMR and Mass spectral analyses. The novel synthesized compounds were screened for their antifungal and antibacterial activities. Compounds 3, 6, 13 and 16 displayed the highest activity against Escherichia coli as revealed from the IC₅₀ values (1.8–1.9 µg/mL). The compound 16 displayed a significant antifungal activity against Candia albicans (0.82 µg/mL), Aspergillus flavus (1.2 µg/mL) comparing to authentic antibiotics. From the TEM microgram, the compounds 3, 12, 13 and 16 exhibited a strong deformation to the cellular entities, by interfering with the cell membrane components, causing cytosol leakage, cellular shrinkage and irregularity to the cell shape. In addition, docking study for the most promising antimicrobial tested compounds depicted high binding affinity against acyl carrier protein domain from a fungal type I polyketide synthase (ACP), and Baumannii penicillin- binding protein (PBP). Moreover, compound 12 showed high drug- likeness, and excellent pharmacokinetics, which needs to be in focus for further antimicrobial drug development. The most promising antimicrobial compounds underwent theoretical investigation using DFT calculation.

Using a simple technique to prepare many uracil derivatives as Schiff base of uracil 4, bis 6-amino[5-(1-(4-aryl)ethylidene)amino)]pyrimidine-2,4-dione 5–12 by heating of 5,6-diamino-1-substituteduracils 1a-e in few drops of DMF with acetophenones by light torch flame and imidazolopyrimidine-2,4-dione 13 which prepared from 5,6-diaminouracil hydrochloride 3a by heating under reflux with 4-bromoacetophenone. Moreover, 6-cyano-7-ethoxypyridopyrimidines 14–16 were prepared by refluxing of 6-amino-1-(2-chlorobenzyl)uracil 1d with ethyl benzylidene cyanoacetate in TEA through conjugate addition followed by intramolecular heterocyclization. All novel synthesized compounds were evaluated for their anticancer activity against three kinds of cancer including liver cancer (HepG2, and Huh7) cell lines, breast cancer (MCF7) cell line, and lung cancer (A549) cell line. Moreover, toxicity of the most cytotoxic compound was evaluated against normal cells (MDCK). Compounds 6, 7, 15, and 16 were the best cytotoxic compounds against most of treated cancer cell lines, and most interestingly they had no toxicity against normal cells. Furthermore, Compound 7 had high binding affinity with cyclin dependent kinase 2 (CDK2), with ability to induce apoptosis in lung cancer cells. Further investigations are needed to elaborate with these novel synthesized compounds with potential cytotoxic activity to develop new effective chemotherapy.

Simple one-pot syntheses of indenopyrrolopyrimidines and indolopyrrolopyrimidines were achieved via the cyclocondensation of 6-aminouracils and, respectively, ninhydrin and isatin in the presence of catalytic amounts of glacial acetic acid. Similarly, 5,6-diaminouracil derivatives were used as starting materials for the synthesis of indenopteridines and indolopteridines via their reaction with ninhydrin and isatin, respectively. The synthesised compounds were evaluated for antitumour activity against a human hepatocellular carcinoma cell line (HepG2), some showing antitumour activity comparable with 5-fluorouracil and imatinib.

Uracil derivatives have a great attraction because they play an important role in pharmacological activities. Pyrimidodiazepines, lumazines, triazolopyrimidines and xanthines have significant wide spectrum activities including anticancer, antiviral as well as antimicrobial activities. A newly synthesized compounds pyrimido[4,5-b][1, 4]diazepines 5a–e, 6a–d, lumazines 7a–d, triazolo[4,5-d]pyrimidine 8 and xanthines 9, 10 was prepared in a good yields. The antimicrobial and antioxidant activities of compounds 5a, 5b, 6a, 6d and 8 exhibited a wide range activity against the pathogenic tested microbes (Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, and Saccharomyces cerevisiae). Compound 8 showed activity against the fungus Aspergillus niger. The highest antioxidant activity was noticed for compound 5a. A series of novel pyrimido[4,5-b][1, 4]diazepines 5a–e, 6a–d, lumazines 7a–d, triazolo[4,5-d]pyrimidine 8 and xanthines 9, 10 was prepared from 5,6-diamino-1-(2-chlorobenzyl)uracil 3 in good yields. Compounds 5a–e, 6a–d were prepared by sequential manipulation of 3 with α,β-unsaturated ketones. Lumazines 7a–d were obtained from 3 by treatment with phenacyl bromides in the presence of TEA. Compound 8 was prepared by treatment of 3 with HNO2, while xanthines 9, 10 were obtained from 3 by consecutive acetylation then intramolecular cyclodehydration or heating with malononitrile under solvent-free condition. The antimicrobial and antioxidant activity of this series was evaluated in vitro and they showed either weak or moderate activities.

Ethyl 5-arylpyridopyrimidine-6-carboxylates 3a–d were prepared as a one pot three component reaction via the condensation of different aromatic aldehydes and ethyl acetoacetate with 6-amino-1-benzyluracil 1a under reflux condition in ethanol. Additionally, condensation of ethyl 2-(2-hydroxybenzylidene) acetoacetate with 6-amino-1-benzyluracil in DMF afforded 6-acetylpyridopyrimidine-7-one 3e; a facile, operationally, simple and efficient one-pot synthesis of 8-arylxanthines 6a–f is reported by refluxing 5,6-diaminouracil 4 with aromatic aldehydes in DMF. Moreover, 6-aryllumazines 7a–d was obtained via the reaction of 5,6-diaminouracil with the appropriate aromatic aldehydes in triethyl orthoformate under reflux condition. The synthesized compounds were characterized by spectral (¹H-NMR, ¹³C-NMR, IR and mass spectra) and elemental analyses. The newly synthesized compounds were screened for their anticancer activity against lung cancer A549 cell line. Furthermore, a molecular-docking study was employed to determine the possible mode of action of the synthesized compounds against a group of proteins highly implicated in cancer progression, especially lung cancer. Docking results showed that compounds 3b, 6c, 6d, 6e, 7c and 7d were the best potential docked compounds against most of the tested proteins, especially CDK2, Jak2, and DHFR proteins. These results are in agreement with cytotoxicity results, which shed a light on the promising activity of these novel six heterocyclic derivatives for further investigation as potential chemotherapeutics.