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Currently, limited therapeutic options are available for severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). We have developed a set of pyrazine‐based small molecules. A series of pyrazine conjugates was synthesized by microwave‐assisted click chemistry and benzotriazole chemistry. All the synthesized conjugates were screened against the SAR‐CoV‐2 virus and their cytotoxicity was determined. Computational studies were carried out to validate the biological data. Some of the pyrazine‐triazole conjugates (5 d–g) and (S)‐N‐(1‐(benzo[d]thiazol‐2‐yl)‐2‐phenylethyl)pyrazine‐2‐carboxamide 12 i show significant potency against SARS‐CoV‐2 among the synthesized conjugates. The selectivity index (SI) of potent conjugates indicates significant efficacy compared to the reference drug (Favipiravir)., Antiviral drug development for SARS‐CoV‐2: The design and microwave‐assisted synthesis of pyrazine conjugates are reported. Some of the newly synthesized conjugates show better antiviral activity and selectivity indexes than those of the reference drug. All the lead compounds exhibited low cytotoxicity. Thus, these conjugates could lead to the development of potential drug candidates for SARS‐CoV‐2.

Background: Bacterial infections are considered as one of the major global health threats, so it is very essential to design and develop new antibacterial agents to overcome the drawbacks of existing antibacterial agents. Method: The aim of this work is to synthesize a series of new fluoroquinolone-3-carboxamide amino acid conjugates by molecular hybridization. We utilized benzotriazole chemistry to synthesize the desired hybrid conjugates. Result: All the conjugates were synthesized in good yields, characterized, evaluated for their antibacterial activity. The compounds were screened for their antibacterial activity using methods adapted from the Clinical and Laboratory Standards Institute. Synthesized conjugates were tested for activity against medically relevant pathogens; Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27856) Staphylococcus aureus (ATCC 25923) and Enterococcus faecalis (ATCC 19433). Conclusion: The observed antibacterial experimental data indicates the selectivity of our synthesized conjugates against E.Coli. The protecting group on amino acids decreases the antibacterial activity. The synthesized conjugates are non-toxic to the normal cell lines. The experimental data were supported by computational studies.

Medicinal plants have curative properties due to the presence of various complex chemical substances of different composition, which are found as secondary metabolites in one or more parts of the plant. The diverse secondary metabolites play an important role in the prevention and cure of various diseases including neurodegenerative diseases like Alzheimer’s disease. Naturally occurring compounds such as flavonoids, polyphenols, alkaloids, and glycosides found in various parts of the plant and/or marine sources may potentially protect neurodegeneration as well as improve memory and cognitive function. Many natural compounds show anti-Alzheimer activity through specific pharmacological mechanisms like targeting β-amyloid, Beta-secretase 1 and Acetylcholinesterase. In this review, we have compiled more than 130 natural products with a broad diversity in the class of compounds, which were isolated from different sources showing anti- Alzheimer properties.

A set of dispiro[indoline-3,2'-pyrrolidine-3',3''-pyrrolidines] 8a-l was regioselectively synthesized utilizing multi-component azomethine cycloaddition reaction of 3-(arylmethylidene)pyrrolidine-2,5-diones 5a-e, isatins 6a-c and sarcosine 7. Single crystal X-ray studies of 8c add conclusive support for the structure. Compounds 8e and 8g reveal cholinesterase inhibitory properties with promising efficacy against both AChE and BChE and were found to be more selective towards AChE than BChE as indicted by the selectivity index like Donepezil (a clinically used cholinesterase inhibitory drug). Molecular modeling studies assist in understanding the bio-observations and identifying the responsible parameters behind biological properties.

We report here the discovery of several highly potent small molecules that showed low nM potency against SARS-CoV (IC50: as low as 13 nM), SARS-CoV-2 (IC50: as low as 23 nM), and MERS-CoV (IC50: as low as 76 nM) in pseudovirus based assays with excellent selectivity indices (SI: as high as > 5000) demonstrating their pancoronavirus inhibition. Some compounds also show 100% inhibition of CPE (IC100) at 1.25 µM against an authentic SARS-CoV-2 (US_WA-1/2020). Furthermore, the most active inhibitors also potently inhibited variants of concerns (VOCs), such as the UK (B.1.1.7), South Africa (B.1.351), and Delta variant (B.1.617.2), originated in India. We confirmed that one of the potent inhibitors binds to the prefusion spike protein trimer of SARS-CoV-2 by SPR. Besides, we showed that they inhibit virus-mediated cell-cell fusion. The ADME data of one of the most active inhibitors, NBCoV1, show drug-like properties. In vivo PK of NBCoV1 in rats demonstrated excellent half-life (t1/2) of 11.3 h, mean resident time (MRT) of 14.2 h, and oral bioavailability. We expect the lead inhibitors to pave the way for further development to preclinical and clinical candidates.

Background: Curcumin is a well-known example of plant origin exhibiting promising diverse biological properties such as, anti-inflammatory and antitumor as well as poor pharmacokinetic/pharmacodynamic properties. This is why effective agents based on its chemical scaffold were explored. Methods: A set of 3,5-bis(ylidene)-1-(alkylsulfonyl)piperidin-4-ones were synthesized in excellent yield (80- 96%) through dehydrohalogenation reaction of 3,5-bis(ylidene)-4-piperidinones with the corresponding alkane sulfonyl chloride in the presence of triethylamine. Antiproliferative properties of the synthesized compounds (dienone/curcumin inspired analogues) were studied by the standard MTT technique. Results: Most of the synthesized compounds revealed antiproliferative properties against HCT116 (colon) and A431 (skin/squamous) cancer cell lines with IC50 values at sub-micromolar level. Compound 36 also exhibited potency against MCF7 (breast) and A549 (lung) cancer cell lines (IC50 = 2.23, 4.27µM, respectively) higher than that of the reference standards (IC50 = 3.15, 5.93µM for 5-fluorouracil and doxorubicin against MCF7 and A549 cell lines, respectively). Cytotoxic properties of the synthesized compounds against non-cancer RPE1 cell line supported the safety profile of the effective agents against normal cells. Molecular modeling (3Dpharmacophore and 2D-QSAR) studies validated the observed bio-properties and explained the parameters governing activity. Inhibitory properties of compounds 27 and 29 (representative examples of the promising antiproliferative agents synthesized) supported their mode of action against topoisomerase IIα Conclusion: The synthesized scaffold is a promising antitumor agent (with special selectivity against colon and skin/squamous cancer cell lines) so, it can be considered for further investigation and development of highly effective hits/leads based on the computational models obtained.

3,5-Bis(arylidene)-N-substituted-4-oxo-piperidine-1-carboxamides 24–51 were synthesized as curcumin mimics in a facile pathway through reaction of 3,5-bis(arylidene)-4-piperidones with the appropriate isocyanate in the presence of triethylamine. The 3E,5E′-stereochemical configuration was conclusively supported by single crystal X-ray studies of compounds 25 and 34. Most of the synthesized piperidinecarboxamides showed high anti-proliferative properties with potency higher than that of 5-fluorouracil (clinically approved drug against colon, breast and skin cancers) through in vitro MTT bio-assay. Some of them revealed anti-proliferative properties at sub-micromolar values (IC50 = 0.56–0.70 μM for compounds 29, 30 and 34–38 against HCT116; and IC50 = 0.64 μM for compound 30 against A431 cell lines) with promising inhibitory properties against human DNA topoisomerase IIα. The safe profile of the anti-proliferative active agents against the RPE1 normal cell line may prove their selectivity towards carcinoma cells. Robust molecular models (2D-QSAR, 3D-pharmacophore) supported the SAR and validated the observed bio-properties.

Graphical abstract Sets of 3-alkenyl-2-oxindoles were synthesized of potential antiproliferative (against PaCa-2 and MCF7cancer cell lines) and promising properties against SARS-CoV-2., Sets of 3-alkenyl-2-oxindoles (6,10,13) were synthesized in a facile synthetic pathway through acid dehydration (EtOH/HCl) of the corresponding 3-hydroxy-2-oxoindolines (5,9,12). Single crystal (10a,c) and powder (12a,26f) X-ray studies supported the structures. Compounds 6c and 10b are the most effective agents synthesized (about 3.4, 3.3 folds, respectively) against PaCa2 (pancreatic) cancer cell line relative to the standard reference used (Sunitinib). Additionally, compound 10b reveals antiproliferative properties against MCF7 (breast) cancer cell with IC50 close to that of Sunitinib. CAM testing reveals that compounds 6 and 10 demonstrated qualitative and quantitative decreases in blood vessel count and diameter with efficacy comparable to that of Sunitinib, supporting their anti-angiogenic properties. Kinase inhibitory properties support their multi-targeted inhibitory activities against VEGFR-2 and c-kit in similar behavior to that of Sunitinib. Cell cycle analysis studies utilizing MCF7 exhibit that compound 6b arrests the cell cycle at G1/S phase while, 10b reveals accumulation of the tested cell at S phase. Compounds 6a and 10b reveal potent antiviral properties against SARS-CoV-2 with high selectivity index relative to the standards (hydroxychloroquine, chloroquine). Safe profile of the potent synthesized agents, against normal cells (VERO-E6, RPE1), support the possible development of better hits based on the attained observations.

Graphical abstract A series of quinolone-triazole conjugates synthesized as potential antiviral agents for SARS-CoV2. Some of the conjugates are more potent than the standards., At present therapeutic options for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are very limited. We designed and synthesized three sets of small molecules using quinoline scaffolds. A series of quinoline conjugates (10a-l, 11a-c, and 12a-e) by incorporating 1,2,3-triazole were synthesized via a modified microwave-assisted click chemistry technique. Among the synthesized conjugates, 4-((1-(2-chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-6-fluoro-2-(trifluoromethyl)quinoline (10g) and 6-fluoro-4-(2-(1-(4-methoxyphenyl)-1H-1,2,3-triazol-4-yl)ethoxy)-2-(trifluoromethyl)quinoline (12c) show high potency against SARS-CoV-2. The selectivity index (SI) of compounds 10g and 12c also indicates the significant efficacy compared to the reference drugs.

Background: A new set of hybrid conjugates derived from 2-(4-isobutylphenyl)propanoic acid (ibuprofen) is synthesized to overcome the drawbacks of the current non-steroidal anti-inflammatory drugs. Results & methodology: Synthesized conjugates were screened for their anti-inflammatory, analgesic and ulcerogenic properties. Few conjugates were found to have significant anti-inflammatory properties in the carrageenan-induced rat paw edema test, while a fair number of conjugates showed promising peripheral analgesic activity in the acetic acid-induced writhing test as well as central analgesic properties in the in vivo hot plate technique. The newly synthesized conjugates did not display any ulcerogenic liability. Conclusion: In vitro, COX-1 and COX-2 enzyme inhibition studies raveled compound 7e is more selective toward COX-2 compared with ibuprofen.

A straightforward, mild and cost-efficient synthesis of various arylamides in water was accomplished using versatile benzotriazole chemistry. Acylation of various amines was achieved in water at room temperature as well as under microwave irradiation. The developed protocol unfolds the synthesis of amino acid aryl amides, drug conjugates and benzimidazoles. The environmentally friendly synthesis, short reaction time, simple workup, high yields, mild conditions and free of racemization are the key advantages of this protocol.

Background Viral diseases are considered main threats that face the humanity worldwide. The emergence of new viruses like influenza viruses emphasizes the significance of designing novel antiviral drugs. Method The aim of this work is to synthesize a new set of nucleoside and non-nucleoside cyanopyridine, characterized and evaluated for their in vitro antiviral properties against various strains. Conclusion More of the compounds showed variable antiviral potential against a panel of eighteen DNA and RNA viruses. The screening data suggested that the order of activity of the active compounds are in the order of O-glycosyl > O-alkyl > N-alkyl > S-alkyl derivatives. In addition, the 4-fluoro substituted compounds are more effective among the O- and N-alkyl analogs, whereas remarkable antiviral activity was ascribed to the methoxylated O-glycosyl derivatives. Most of the active compounds proved to be more selective towards the inhibition of the replication of DNA rather than the RNA-viruses. The analogs 1a, 2a, 12b, 14b and 16b possessed broad spectrum and noticeable antiviral potential against most of the tested DNA- and RNA-viruses (EC50 ≈ 0.8-20 µM), accompanied with considerably low cytotoxic margin (MCC ≈ 4-20 µM), and comparable with reference standard antiviral agents.

Twenty-five valproic acid conjugates have been designed and synthesized. All target compounds were explored for their in vitro anti-proliferative activities using the MTT-based assay against four human cancer cell lines includingliver (HePG2), colon (HCT116), breast (MCF7) and cervical (HeLa) carcinoma cell lines. Out of six valproic acid-amino acid conjugates 2a-f. Only cysteine containing conjugate 2f showed the significant activity (IC50 9.10 µM against HePG2 and 6.81 µM against HCT116). However conjugate 2j showed broad-spectrum antitumor activity against all cell lines tested. In addition, conjugates 4j and 4k which contains phenyl hydrazide and hydroxamic acid group, respectively, also showed broad spectrum activity. Furthermore, six compounds were screened for HDAC 1-9 isozymes inhibitory activities. Compounds 2j, 4j and 4k manifested a higher inhibitory activity more than valproic acid but less than SAHA. In addition, the in vivo antitumor screening of 2j, 4j and 4k was done and the results have shown that 2j, 4j and 4k, particularly 4j, showed a significant decrease in tumor size and presented a considerable decrease in viable EAC count. Docking study of selectedcompound 4j revealed that it can bind nicely to the binding pocket of HDAC 1, 2, 3, 4 and HDAC 8. The results suggest that compounds 2j, 4j and 4k, particularly 4j, may be promising lead candidates for the development of novel targeted anti-tumor drug potentially via inhibiting HDACs.

A set of 1,2,3-triazole incorporated quinolone antibiotic conjugates 10–15, 17–19 were synthesized via microwave assisted click chemistry technique. Some of the aryl-substituted conjugates 17–19 show promising antibacterial properties against the tested Gram-positive (S. aureus and S. pyogenes) and Gram-negative bacteria (S. typhi) with potency higher than that of the parent antibiotics 1–3. 2D-QSAR modeling supports the observed biological properties.

Graphical abstract Series of salicylate-curcumin mimics were synthesized of potential antiproliferative (against A431 and HCT116 cell lines) and anti-SARS-CoV-2 properties., Series of piperidone-salicylate conjugates were synthesized through the reaction of 3E,5E-bis(arylidene)-4-piperidones with the appropriate acid chloride of acetylsalicylate in the presence of triethylamine. All the synthesized conjugates reveal antiproliferative properties against A431 (squamous skin) cancer cell line with potency higher than that of 5-fluorouracil. Many of the synthesized agents also exhibit promising antiproliferative properties against HCT116 (colon) cancer cell line, of which 5o and 5c are the most effective with 12.9, 9.8 folds potency compared with Sunitinib. Promising activity is also shown against MCF7 (breast) cancer cell line with 1.19, 1.12 folds relative to 5-fluorouracil. PI-flow cytometry of compound 5c supports the arrest of cell cycle at G1-phase. However, compound 5o and Sunitinib arrest the cell cycle at S-phase. The synthesized conjugates can be considered as multi-targeted tyrosine kinase inhibitors due to the promising properties against VEGFR-2 and EGFR in MCF7 and HCT116. CDOCKER studies support the EGFR inhibitory properties. Compounds 5p and 5i possessing thienylidene heterocycle are anti-SARS-CoV-2 with high therapeutic indices. Many of the synthesized agents show enhanced COX-1/2 properties than aspirin with better selectivity index towards COX-2 relative to COX-1. The possible applicability of the potent candidates discovered as antitumor and anti-SARS-CoV-2 is supported by the safe profile against normal (non-cancer, RPE1 and VERO-E6) cells.

Facile synthetic pathway for nicotinonitriles 5a‒o, 7a‒i was demonstrated through reaction of ketones 4a‒k, 6a‒f with ylidenemalononitrile 3 in the presence of sodium alkoxide. Meanwhile, nucleophilic attack of amines on 2-bromonicotinonitrile 9 (obtained through reaction of propenone 8 with malononitrile, followed by bromination with bromine in acetic acid) afforded 3-pyridinecarbonitriles 11a‒d. Single crystal X-ray of compound 7i reveals the monoclinic space group C2/c with 8 molecules per unit cell. Optimized structure of 7i [DFT/B3LYP, 6-31G(d,p)] shows close correlations to that of X-ray study. Compound 5l seems superior among all the synthesized analogues exhibiting bronchodilation properties about three folds potency compared to theophylline (standard reference) through pre-contracted tracheal rings with histamine standard method. Also compound 5a reveals promising observations (about two folds potency of the standard reference). Molecular modeling studies (3D-pharmacophore and 2D-QSAR) supported the observed biological properties.

Benzotriazole-activated pyrazinoic acid was utilized as a versatile building block for the efficient and convenient synthesis of novel hybrid conjugates of pyrazinoic acid with secondary amines via amino acid linkers in high yields.

A series of new fluoroquinolone conjugates 8a-g and 9a-f were synthesized via benzotriazole-mediated synthetic approach with good yield and purity. Some of the synthesized analogs exhibited significant antibacterial properties against Escherichia coli and Staphylococcus aureus with potency higher than that of the parent drugs through in vitro standard bioassay procedure (conjugates 8c and 8d reveal antimicrobial properties with potency 1.9, 61.9, 20.7 and 2.4, 37.1, 8.3 folds relative to the parent antibiotic 6 against E. coli, S. aureus, and Enterococcus faecalis, respectively). The observed experimental data were supported by enzymatic DNA gyrase inhibitory property. Developed BMLR-QSAR model validates the observed experimental data and recognizes the parameters responsible for the enhanced antibacterial properties.

A Facile synthetic approach is reported towards 4-hydroxyquinazoline-4-carboxamides 13a–i through ring expansion of 2,3-dioxoindoline-1-carboxamides 10a–c during secondary amine 11a–d nucleophilic reaction. Single crystal X-ray studies of 10c and 13d support the structures. Some of the synthesized quinazolinecarboxamides 13 show promising vasorelaxant properties with potency higher than that of Doxazosin through the pre-contracted (norepinephrine hydrochloride) rat aorta standard bioassay. Good molecular models (2D-QSAR, pharmacophore) describe the biological observations.

Benzotriazole and microwave mediated syntheses led to a new set of hybrid conjugates of pyrazinoic acid with isoniazid via amino acid linkers in excellent yields with retention of chirality. Microbiological screening of the synthesized conjugates revealed an exceptionally high activity against some of the pathogenic bacterial strains at low concentrations. Promising antimycobacterial properties were observed against tuberculous and non-tuberculous mycobacteria. Robust molecular models (2D-QSAR and 3D-pharmacophore) support the observed biological properties. Safety profile of the synthesized conjugates against human normal cell (RPE1) was evaluated by MTT technique.

This work deliberates to provide compatible ink for restoration of faded manuscripts. Four writing inks Virdgris, Carbon black, Almond shell and iron galls were prepared based on traditional formulations. The inks were characterized using FTIR, XRF, UV–vis spectrometer techniques. The color characterization technique was done to ensure color stability of the prepared inks. The elemental data showed potassium as a major component for the almond shell (54.42 wt%) and carbon black (24.01 wt%) whereas copper and iron is major element for Verdigris and iron gall inks (>98 wt%), respectively with Mn, Ca, S and Zn as minor components. The Fourier transform infrared (FTIR) spectrum showed different components are present in the prepared inks. The inks were applied on four different substrate birch bark, palm leaves, handmade paper, and papyrus to elucidate their writing efficacy and color stability. The Commission Internationale de l’Eclairage (CIE) L*a*b* color space parameter was applied to measure the color stability for a regular period. The total color differences ΔE* ab was calculated using L*, a*, and b* data. The color index studies at the regular intervals carried to monitor color difference and surface reflectance. All the substrates were further passed through accelerated weathering test and total color difference ΔE* ab, CIE L* a*b* was again calculated using L*, a*, and b* to know the color stability. Based on the analytical data, these natural and stable inks can be recommended for archival manuscript conservation particularly in retouching operation by adjusting other parameters.

The mechanical strength of cellulose is related to its fibre-to-fibre bonding ability within the structural moiety. The present work summarises the strength of the representative handmade papers of high and low grams per square meter (GSM) value currently used in the conservation of archival material by assess their fibre network, morphology, elemental composition and bonding ability within the cellulose network. The bonding ability of thee handmade papers has been studied using fourier-transform infrared spectroscopy (FTIR) spectrum and further study of these spectra between bonded and free OH group within the OH stretching vibrational region. The intermolecular hydrogen bonding ability for Nepalese tissue paper is 2.14 and intramolecular hydrogen bonding is 1.66. The hydrogen bond energy of these papers were between 13 kJ and 29 kJ, calculated on the basis of H-bonding behaviour. The morphology provides flat and sheet-like layers in the networking structure studied with environmental scanning electron microscope (ESEM) and mapping was done for each element. Carbon and Oxygen are the major elements associated in these papers whereas Ca, Cl, Si, Mg, Na, S and Al are present as minor elements in these papers. Results of both the covalent bonding ability and morphology are well correlated.

Microwave-mediated one-step synthesis of several bi- and tricyclic heterocycles via the intermolecular cyclization of N -acylbisbenzotriazoles with ortho -phenylenediamine in good yield is reported.

1,4-Disubstituted-1,2,3-triazoles were synthesized by Cu(I) catalyzed click reaction, where the azides, with electron donating and electron withdrawing groups acted as 1,3-dipoles and 1-ethynyl-1-cyclohexanol served as the terminal alkyne. These synthesized triazoles were subjected to enzymatic assay which showed promising activity against α-glucosidase; 1-(2-cyano-4-nitrophenyl)-4-(1-hydroxycyclohexyl)-1H-1,2,3-triazole 3m being the most active members of the library. Molecular docking studies of these triazoles with the homology-modeled α-glucosidase protein were also performed to delineate ligand-protein interactions at molecular level which suggested that Phe157, Arg312 and His279 are the major interacting residues in the biding site of the protein and may have a significant role in the inhibition of enzyme's function.

Indole-based compounds 30–63 were synthesized by the multi-component 1,3-dipolar cycloaddition reaction of 1-alkyl-3,5-bis(arylidene)-4-piperidones 11–25 with azomethine ylides (generated by the condensation of isatins 26–28 with sarcosine 29). The single crystal X-ray studies of 46 and 48 supported the regio- and stereoselectivity of the reaction. Most of the synthesized spiro-indoles exhibited potent antitumor properties against the HeLa (cervical cancer) cell line through in vitro sulfo-rhodamine-B bioassay, higher than that of cisplatin. Only compound 54 showed bio-potency against the HepG2 (hepatocellular cancer) cell line, comparable to that of doxorubicin hydrochloride (standard reference). 3D-Pharmacophore and 2D-QSAR studies were used to validate the observed biological data and determine the most important parameters controlling activity. The estimated bio-properties from the computational studies showed high approximations to the experimental data.

Two sets of diphenyl ether derivatives incorporating five-membered 1,3,4-oxadiazoles, and their open-chain aryl hydrazone analogs were synthesized in good yields. Most of the synthesized compounds showed promising in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv. Three diphenyl ether derivatives, namely hydrazide 3, oxadiazole 4 and naphthylarylidene 8g exhibited pronounced activity with minimum inhibitory concentrations (MICs) of 0.61, 0.86 and 0.99 μg/mL, respectively compared to triclosan (10 μg/mL) and isoniazid (INH) (0.2 μg/mL). Compounds 3, 4, and 8g showed the InhA reductase enzyme inhibition with higher IC50 values (3.28–4.23 µM) in comparison to triclosan (1.10 µM). Correlation between calculated physicochemical parameters and biological activity has been discussed which justifies a strong correlation with respect to the inhibition of InhA reductase enzyme. Molecular modeling and drug-likeness studies showed good agreement with the obtained biological evaluation. The structural and experimental information concerning these three InhA inhibitors will likely contribute to the lead optimization of new antibiotics for M. tuberculosis.

Aim: Synthesis of novel bronchodilatory active indole–pyridine conjugates. Results/methodology: Indole–pyridine conjugates (6a–n, 8a–i and 10a–c) were synthesized in a facile pathway through reaction of 2-[(1-alkyl-1H-indol-3-yl)methylene]malononitriles 4a,b with the corresponding ketone-containing compounds (5a–f, 7a–c and 9a,b) in the presence of sodium alkoxide. Single (6l, 8 g) and powder (6k, 8d) x-ray studies supported the structures. Results: Histamine precontracted isolated tracheal rings of guinea pig exhibited the potent bronchodilation properties of 6c (about double-fold potency relative to the standard reference, theophylline). Some of the synthesized conjugates (8d, 6c, 6f and 6e) revealed promising reduction of IL-8 production during lipopolysaccharide-induced airway inflammatory bioassay. Computational studies (3D pharmacophore, 2D-QSAR ‘quantitative structure–activity relationship’) showed high approximations to the bronchodilation properties and explained the parameters controlling biological observations.

Chiral peptides and iso-peptides were synthesized in excellent yield by using benzotriazole mediated solution phase synthesis. Benzotriazole acted both as activating and leaving group, eliminating frequent use of protection and subsequent deprotection. The procedure was based on the hypothesis that epimerization should be suppressed in solution due to a faster coupling rate than SPPS. All the synthesized peptides complied with Lipinski's Ro5 except for the rotatable bonds. Inhibition of cell proliferation of cancer cell lines is one of the most commonly used methods to study the effectiveness of any anticancer agents. Synthesized peptides and iso-peptides were tested against three cancer cell lines (MCF-7, MDA-MB 231) to determine their anti-proliferative potential. NFkB was also determined. Molecular docking studies were also carried out to complement the experimental results.

Novel, mesalazine, metronidazole conjugates 6a – e with amino acid linkers were synthesized utilizing benzotriazole chemistry. Biological data acquired for all the novel bis-conjugates showed (a) some bis-conjugates exhibit comparable anti-inflammatory activity with parent drugs and (b) the potent bis-conjugates show no visible stomach lesions. 3D-pharmacophore and 2D-QSAR modeling support the observed bio-properties.

Single crystal X-ray studies of regioselectively synthesized fluoro-substituted dispiro-oxindole 9 revealed that the structure belongs to the monoclinic space group P21/n with four molecules in the unit cell. The structure was also investigated by AM1, PM3, and DFT studies. Compound 9 exhibits high potency against the HeLa cell line.

Novel, cyclic peptidomimetics were synthesized by facile acylation reactions using benzotriazole chemistry. Microbiological testing of the synthesized compounds revealed an exceptionally high activity against Candida albicans with a minimum inhibitory concentration (MIC) two orders of magnitude lower than the MIC of the antifungal reference drug amphotericin B. A strikingly high activity was also observed against three Gram-negative bacterial strains (Pseudomonas aeruginosa, Klebsiella pneumoniae and Proteus vulgaris), two of which are known human pathogens. Thus the discovered chemotype is a potential polypharmacological agent. The toxicity against mammalian tumor cells was found to be low, as demonstrated in five different human cell lines (HeLa, cervical; PC-3, prostate; MCF-7, breast; HepG2, liver; and HCT-116, colon). The internal consistency of the experimental data was studied using 3D-pharmacophore and 2D-QSAR.

Antitumor active dispiro[3H-indole-3,2′-pyrrolidine-3′,3′′-piperidine]-2(1H),4′′-diones 11–19 were regioselectively synthesized via azomethine ylide cycloaddition reactions with 3E,5E-1-alkyl-3,5-bis(arylmethylidene)-4-piperidones 3–7. Compounds 13, 14, and 16 reveal higher potency against the HeLa (cervical) tumor cell line than the standard reference cisplatin, while 11, and 12 seem more potent against the HepG2 (liver) carcinoma cell line relative to the standard reference doxorubicin hydrochloride as determined by in vitro Sulfo-Rhodamine-B bio-assay. 3D-Pharmacophores of the HeLa comprise five chemical features viz., two hydrogen bond acceptors, two hydrophobic centers and one positive ionizable center and HepG2 contains three chemical features viz., a hydrogen bond acceptor, a hydrophobic center and a positive ionizable center. These features of the tumor cell lines explain the variation of bioactivity relative to chemical structure. Statistically significant QSAR models describing the spiro-alkaloid bio-properties were obtained employing CODESSA-Pro software validating the observed pharmacological observations and identifying the most important parameters governing activity.

3D-pharmacophore and 2D-QSAR modeling studies describe the anti-oncological properties of spiro-alkaloids. The dispiro[2H-indene-2,3'-pyrrolidine-2',3''-[3H]indole]-1,2''(1''H, 3H)-diones 20-38 were prepared via 1,3-dipolar cycloaddition reactions of azomethine ylides (generated in situ via decarboxylative condensation of isatins 7-9 with sarcosine 10) and 2-(arylmethylidene)-2,3-dihydro-1H-inden-1-ones 11-19 in refluxing ethanol. Some of the spiro-alkaloids (21, 22, 29 and 37) revealed potent antitumor properties against melanoma carcinoma cell lines (GaLa, LuPiCi and LuCa) utilizing the in vitro SRB standard method exhibiting potency close to that of the standard reference doxorubicin.

A procedure for the cyclization of dipeptidoyl benzotriazolides containing proline derivatives promoted by triethylamine under MW activation is introduced. The reaction is general for a variety of dipeptidoyl benzotriazolides and represents a very practical and convenient method for the preparation of Pro- or Hyp-derived 2,5-diketopiperazines (2,5-DKPs) and bis-DKPs with a disulfide linker. This method can be used for the construction of 2,5-DKP compound libraries and for the synthesis of natural products with diketopiperazine cores.

The spiroindole heterocyclic scaffold is found in many natural products and has been identified as an important bioactive agent. Over the past few decades, various spiroindole-containing compounds have been reported to possess biological properties and hence found in the structure of many synthetic pharmaceuticals. This mini-review describes the most promising examples of this class of compounds possessing biological activity including anticancer, anti-inflammatory, and antimicrobial activities. To the best of our knowledge, the earlier reviews did not cover the pharmaceutical properties of synthetic and naturally occurring spiroindoles; thus, the current review focuses on the biological activity of compounds containing the spiroindole scaffold.

Protected arginine thioacid enables convenient N-acylation with no detectable racemization. We report efficient syntheses of potentially biologically active arginine conjugates and novel arginine-containing di-, tri- and tetrapeptides in good yields without loss of chiral integrity.

Two approaches to the synthesis of oxygen-bridged tetrahydropyridones have been developed. In the first approach, substituted pyrido[4,3-g][1,3]oxazocines derivatives were prepared by diastereoselective one-pot reactions of substituted 7-azacoumarins with enolizable ketones and non-bulky primary amines. In the second one, 3-amido-7-azacoumarins were reacted with enolizable ketones in the presence of a base to form diastereomerically pure pyrido[4,3-g][1,3]oxazocines.

Benzotriazole surrogates showing higher stabilities than the corresponding chlorophosphates, allow phosphonylation of a variety of N-, O-, and S-nucleophiles in good yields.

N-Acyl threonine isopeptides undergo acyl transfer in chemical ligations via 5-, 8-, 9and 10membered cyclic transition states to yield natural peptides, representing the first examples of successful isopeptide ligations from N-acyl threonine units.

Benzotriazole-mediated synthesis provides novel fluorescent-labeled amino acid–quinolone antibiotic conjugates in good yields with retention of chirality. The photophysical properties of all the fluorescent-labeled antibiotic conjugates were determined.

Benzotriazole-activated biotin was utilized as a versatile building block for the efficient and convenient synthesis of novel biotin conjugates with quinolone antibiotics via amino acid linkers under microwave irradiation. The products are obtained in yields of 70–91% with retention of chirality.