Design, Synthesis and Biological Investigation of Some Novel Quinazolin-4(3H)-One Tethered 1, 3, 4-Thiadiazole-Thiol Motifs as Direct Enoyl Acyl Carrier Protein Reductase Inhibitors

Aims: In this study was two noteworthy pharmacophores quinazolin-4(3H)-one and 1,3,4-thiadiazole through methylene bridge were utilized to design, synthesize and characterize some novel 2-methyl quinazolin-4(3H)-one and 6-chloro-2-methyl quinazolin-4(3H)-one tethered S-substituted-1,3,4-thiadiazole-thiol structural analogs respectively as direct Mycobacterium Tuberculosis (MTB) enoyl acyl carrier protein reductase (InhA) inhibitors. Study Design: Design of structural analogs of quinazolin-4(3H)-one tethered 1,3,4-thiadiazole-thiol through methylene bridge by functional group modifications in core scaffold followed by computational studies to select promising compounds. Synthesis of some novel compounds, structural characterization and screening of biological activity of the same. Methodology: The molecular docking of designed compunds was carried out using schrodinger Glide XP into the active site of MTB InhA with protein data bank code (PDB ID: 2H7M). The interactions were evaluated based on the glide G score compared with reference standard isoniazid. Ten new compounds 7(A1-A10) were synthesized, characterized and screened for their in-vitro antitubercular activity by Microplate Almar Blue Assay (MABA) method followed by cytotoxicity evaluation of compounds 7A4 and 7A10 using Vero cell line. Results: All the designed compounds of series 7(A1-A10) had drug-like characteristics and were non-toxic to normal cells. In the molecular docking studies, compounds 7A4, 7A5, and 7A10 demonstrated strong binding affinity in the active region of MTB InhA protein and retained necessary amino acid interaction, similar to co-crystal 2H7M. Synthesized compounds 7(A1-A10) were found to have good antitubercular activity. Out of the series the compounds 7A4 and 7A10 were found to possess excellent antitubercular activity equipotent to reference standard streptomycin with minimum inhibitory concentration (MIC) value of 6.25µg/ml. The cytotoxic potential of compounds 7A4 and 7A10 showed remarkable selectivity index against Vero cell line. Conclusion: The findings of this study highlights the importance of tethering two pharmacophoric motifs in one compound to develop novel antitubercular agents that can be exploited as promising leads as direct InhA inhibitors.

ALTERNATIVE METHODS OF SYNTHESIS OF NOVEL HETEROSYNTHONES – FUNCTIONALIZED HYPOXANTHINE PYRIMIDINES

It has been known that derivatives of dihydropyrimidine and xanthine possess the physiological activity of the wide spectrum of action. The combination of the specified heterocyclic fragments within one molecule can lead to the increase of its known types of biological activity as well as to the discovery of novel types of activity. We have previously reported the synthesis of intermediates, which consist of functionalized dihydropyrimidines, connected via a methylene bridge with the halogen substituted derivatives of the ophylline, 3-methylxanthine and imidazole. It was also observed that these compounds would react with N‑nucleophiles with the formation of various branched and cyclic products. The aim of this work was to determine the optimal conditions for obtaining heterocyclic products as a result of conjugation of bromomethyldihydropyrimidine and hypoxanthine at the positions C6 and C1 via a methylene bridge. It is important to note, that the latter can be widely modified by using structurally diverse aromatic aldehydes during the synthesis of dihydropyrimidine core by using Biginelli reaction, which explains structural diversity of the reaction products. After having tried various reaction conditions, we have concluded that the optimal method for obtaining the products entailed keeping equimolar ratios of bromomethyl substituted dihydropyrimidines and 1-potassium‑2-chloro‑7-methylhypoxanthine in dry ethanol for 4 hours. The ester group at the C5 of dihydropyrimidine ring and a chlorine leaving group at C2 of hypoxanthine fragments of the molecule allow to consider these structures as pro missing synthons for farther synthesis of condensed pyrimidine and xanthine systems. The structures of novel compounds have been confirmed with the methods such as HPLC/MS, 1H, and 13C NMR spectroscopy.

Synthesis of Enantiopure ω-(4-Fluorophenyl) 6,11-Methylene Lipoxin B4 Methyl Ester

The synthesis of Lipoxin B4 analogs (LXB4) to gain access to stabilized inflammation resolving compounds is an active field of research. Focusing on variation and stabilization of the conjugated E,Z,E,E C6–C13 tetraene moiety of natural LXB4, a methylene bridge introduced between C6 and C11 suppresses any Z/E isomerization of the C8–C9 olefin. Furthermore, rapid ω-oxidation (C20) should be avoided by replacing the C18-C20 segment by an aromatic moiety. Optically active C1–C12 building blocks were accessed from cycloheptatriene 1-carbonester (C6–C11, C21) and glutaryl chloride (C1–C5) as described earlier. The ω-segment had been generated via a five-step sequence starting from 4-arylbutanoic acid. Horner key olefination enabled assembly of the carbon backbone. A final five step sequence including a chelate Cram reduction of the unsaturated ketone moiety afforded the target ω-aryl 6,11-methylene-LXB4 methyl ester.

An Integrated LC-ESI-MSn and High Resolution LC-ESI-QTOF Approach for the Identification of Phloroglucinols from Nepalese Hypericum japonicum

Phloroglucinols are characteristic constituents of Hypericumjaponicum that are claimed to exert several bioactivities, such as anti-inflammatory, anti-depressant and anti-viral ones. Phloroglucinols are unstable compounds and their synthesis is challenging; thus, isolation from natural sources is still one of the main strategies for obtaining these constituents in purified form. Assessing the presence of phloroglucinols in plant materials can be of interest for compound isolation, and LC-MS approaches afford sensitivity and specificity in this regard. In this work, we combined data from quadrupole-time of flight (QTOF) and ion trap (IT) mass spectrometers in order to assess the presence of the phloroglucinols characteristic of H. japonicum and to elucidate their MS fragmentation pathways. The identified compounds present similar structures bearing the 1,3,5-trihydroxybenzene core with different substitutions, which, in constituents at higher MW, is linked to 3′,3′-dimethyl-6′-oxo-phlorisobutyrophenone by a methylene bridge. Differences in MS2 spectra of the considered phloroglucinols are useful for compound identification and differentiation, and to perform dereplication studies. Overall, the proposed approach could be useful for the analysis of phloroglucinols in H. japonicum and other plant species.

Synthesis and antiviral properties of 1-substituted 3-[ω-(4-oxoquinazolin-4(3h)-yl)alkyl]uracil derivatives

А series of uracil derivatives containing a 4-oxoquinazoline fragment bound to the nitrogen atom N3 of the pyrimidine ring by a short methylene bridge was synthesized to search for new antiviral agents. Some compounds in this series are shown to exhibit high inhibitory activity against human cytomegalovirus and the varicella zoster virus in a HEL cell culture.

Grinding Technique on Synthesis of Calixarene and Its Derivatives

The synthesis of p-t-butylcalix[6]arene (PK[6]A) and calixresorcinarene derivative compounds, namely C-para-dimethylamino-phenylcalix[4]resorcinarene (CPDAK[4]R) and C-4-hydroxy-phenylcalix[4]-resorcinarene (CHK[4]R), had been carried out by grinding technique. The grinding technique was done with the absence of solvents so that it minimized the waste. Synthesis occurred through electrophilic substitution reactions with KOH as an alkaline catalyst and p-toluene sulfonic acid as an acid catalyst. The three calixarene products were in the form of crystalline solids with a melting point of more than 300°C, insoluble in water with yields of 62.58; 61.94 and 97.49%, respectively. Product characterization using FTIR analysis showed the vibration of the methylene bridge (-CH2-) at a wavenumber of 1473.62 cm-1 and LC-MS analysis for (PK[6]R) showed that the molecular weight was 974.77 g/mole. While the analysis of (CPDAK[4]R) and (CHK[4]R) with 1H NMR showed the presence of protons from the methine bridge (-CH-) that appear at the chemical shift of 4.950 and 3.078 ppm.