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In this review, we have summarised the significant advances made in triazine-based COP synthetic strategies and their catalytic advancements. Synthetic methodologies are discussed in a simplistic way to create a better understanding for future modification of these methods.

Simple ammonium ionic liquids [ILs] are efficient, green, environmentally friendly catalysts in promoting the Biginelli condensation reaction, Hantzsch reaction and Niementowski reaction to afford 1,2,3,4-tetrahydropyrimidine, 2-aminothiazole and quinazolinone derivatives respectively by eliminating the need for harmful volatile organic solvents. These [ILs] are air and water stable, easy to prepare and cost-effective. The effects of the anions and cations present in [IL] on reactions were investigated. The results clearly indicated that the Biginelli condensation reaction, Hantzsch reaction and Niementowski reaction were heavily influenced by the acidity of [IL], and among various ammonium ionic liquids, [Et3NH][HSO4] showed the best catalytic activity. Furthermore, [IL] could be easily separated and reused with a slight loss of its activity. This technique provided a good alternative way for the industrial synthesis of 1,2,3,4-tetrahydropyrimidinones, 2-aminothiazoles and quinazolinones. The present processes are eco-friendly methods for the synthesis of these derivatives authenticated by several green parameters, namely, E-factor, process mass intensity, reaction mass efficiency, atom economy, and carbon efficiency.

The artemisinin resistance has posed a serious threat against malaria elimination lately. Past few years have seen important development of several peroxide based medicinal compounds and their derivatives such as trioxanes and tetraoxanes. Here, we report a rapid, one-pot method for synthesizing a new series of N-sulfonylpiperidine dispiro-1,2,4,5-tetraoxane analogs with diverse substitution on the tetraoxane ring i.e., various substituted alkyl and aryl sulfonyl chlorides, as well as cyclic, acyclic and aryl substituted ketones. All the synthesized tetraoxanes were characterized by spectroscopic (

Synthesis of thienoindoles via easy and atom economical approaches followed by their potent applications.

Sulfonic acid functionalized over biguanidine fabricated silica-coated heterogeneous magnetic nanoparticles (NP@SO3H) have been synthesized, well characterized and explored for the first time, as an efficient and recyclable catalyst for N-formylation of primary amines under mild reaction conditions. Exploiting the magnetic nature of Fe3O4, the prepared catalyst was readily recovered from the reaction mixture via an external magnet. The catalyst can be reused for up to six cycles without any substantial loss of catalytic activity. The cost effectiveness, simple methodology, wide substrate tolerance, excellent yield and easy work-up are the additional advantages of present catalytic system.

Sulfonic acid functionalized over biguanidine fabricated silica-coated heterogeneous magnetic nanoparticles (NP@SO

Mechanistic insights into the interaction of five previously chemically synthesized triazole-linked chalcone analogs (CTs) with human serum albumin (HSA) were sought using various spectroscopic techniques (UV-visible absorption, fluorescence, and circular dichroism) and molecular docking. The fluorescence quenching experiments performed at three different temperatures (288, 298 and 308 K) revealed the static mode of quenching and the binding constants (Kb ∼ 106–9) obtained indicated the strong affinity of these analogs for HSA. Furthermore, significant changes in the secondary structure of HSA in the presence of these analogs were also confirmed by far UV-CD spectroscopy. The thermodynamic properties such as the enthalpy change (ΔH°), Gibbs free energy change (ΔG°) and entropy change (ΔS°) revealed that the binding process was spontaneous and exothermic. Theoretical studies, viz., DFT and molecular docking corroborated the experimental results as these five analogs could bind with HSA through hydrogen bonding and hydrophobic interactions. The present study provides useful information regarding the interaction mechanism of these analogs with HSA, which can provide a new avenue to design more potent chalcone triazole analogs for use in the biomedical field.

The interaction of triazole substituted 4-methyl-7-hydroxycoumarin derivatives (CUM1-4) with serum albumin (bovine serum albumin [BSA] and human serum albumin [HSA]) have been studied employing ultraviolet-visible (UV-Vis), fluorescence, circular dichroism (CD) spectroscopy, and molecular docking methods at physiological pH 7.4. The fluorescence quenching occurred with increasing concentration of CUMs, and the binding constant of CUM derivatives with BSA and HSA obtained from fluorescence quenching experiment was found to be ~ 104 L mol-1 . CD study showed conformational changes in the secondary structure of serum albumin upon titration of CUMs. The observed experimental results were further validated by theoretical studies involving density functional theory (DFT) and molecular docking.

Explosives can be classified into nitroaromatic compounds (NACs), nitrate esters, nitramines and peroxides. Among these, NACs are at the center of extensive literature studies. NACs are stable and useful in many military operations. However, their stability and explosiveness comes with an ever-increasing danger pertaining to their illegitimate use in terrorist activities. Moreover, NACs are toxic, mutagenic and carcinogenic, and hence they need to be screened out of the environment before their levels reach the admissible limits. The development of economical, efficient, sensitive and real-time sensors for combating the threat of NACs is the greatest need of the hour. In this review, we provide a comprehensive discussion of the recent advancements in the field of NAC sensors.

An ecofriendly, magnetically retrievable amine-functionalized SiO2@Fe3O4 catalyst was successfully synthesized and affirmed by several physicochemical characterization tools, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDX), and powder X-ray diffraction. Thereafter, the catalytic performance of this environmentally benign NH2@SiO2@Fe3O4 catalyst was investigated in the one-pot multicomponent synthesis of 2-amino-4H-benzo[b]pyran derivatives. The reaction was simply achieved by grinding of various substituted aromatic aldehydes, dimedone, and malononitrile at room temperature under solvent and waste-free conditions with excellent yields and high purity. Moreover, the developed catalyst not only possesses immense potential to accelerate the synthesis of bioactive pyran derivatives but also exhibits several remarkable attributes like broad functional group tolerance, durability, improved yield, reusability, and recyclability. Besides, various other fascinating advantages of this protocol are milder reaction conditions, cost effectiveness, short reaction time, and simple work up procedures.

This work represents the design and synthesis of efficient sulfonated cobalt ferrite solid acid catalyst. The synthesized solid acid green catalyst was characterized using various techniques viz. FT-IR, powder XRD, SEM, TEM and VSM. The obtained catalyst was used to synthesize biologically significant 2-substituted benzimidazole derivatives by condensation between o-phenylenediamine with various aromatic, aliphatic and heterocyclic aldehydes. High yield (up to 98 %), short reaction time (10−25 min), mild reaction condition, wide functional group tolerance, easy work-up procedure and excellent values of green chemistry metrices such as lower E factor (0.126), high RME value (88.83 %), carbon efficiency (100 %) and high atom economy (AE) value (90.65 %), are some salient features of the present catalytic system. Moreover, the catalyst recovery by simply using an external magnet and catalyst reusability up to 7 times without any significant loss in catalytic efficiency are some additional remarkable features of the current protocol.

A new simple and efficient fluorous coupling reagent TriTFET (2,4,6-tris-(2,2,2-trifluoro-ethoxy)-[1,3,5] triazene) has been designed and synthesized for the direct amidation. The use of 5 mol % of TriTFET is good for the amide synthesis from carboxylic acids with amines in moderate to excellent yields (72–96%).

A very efficient chiral organocatalyst was prepared from the readily available cyanuric chloride. The asymmetric catalyst exhibited a highly enantioselective catalytic performance for the alkylation of a glycinate Schiff base, which provides a useful procedure for the enantioselective synthesis of structurally diverse natural and unnatural α-alkyl-α-amino acids.

A pyrene-based optical probe for the real-time and regenerative detection of Cu2+ and Fe3+ at parts-per-million (ppm) levels is demonstrated. Moreover, the quantifiable changes in the fluorescence signal induced by chemical inputs viz. Cu2+, Fe3+, H+ and CN− have been exploited to assemble sequential and “four-input” combinatorial molecular logic circuits. A unique “two-way” security lock has also been devised for enhanced information protection at the molecular level.

Emergence of drug-resistant Plasmodium falciparum strains has led to a situation of haste in the scientific and pharmaceutical communities. Hence, all their efforts are redirected toward finding alternative chemotherapeutic agents that are capable of combating multidrug-resistant parasite strains. In light of this situation, scientists have come up with the concept of hybridization of two or more active pharmacophores into a single chemical entity, resulting in “antimalarial hybrids.” The approach has been applied widely for generation of lead compounds against deadly diseases such as cancer and AIDS, with a proven potential for use as novel drugs, but is comparatively new in the sphere of antimalarial drug discovery. A sudden surge has been evidenced in the number of studies on the design and synthesis of hybrids for treating malaria and may be regarded as proof of their potential advantages over artemisinin-based combination therapy (ACT). However, it is evident from recent studies that most of the potential advantages of antimalarial hybrids, such as lower toxicity, better pharmacokinetics, and easier formulation, have yet to be realized. A number of questions left unaddressed at present need to be answered before this approach can progress to the late stages of clinical development and prove their worth in the clinic. To the best of our knowledge, this compilation is the first attempt to shed light on the shortcomings that are surfacing as more and more studies on molecular hybridization of the active pharmacophores of known antimalarials are being published.

Ceric ammonium nitrate (CAN) is found to be a suitable, inexpensive, and effective non-toxic catalyst for a smooth (3+2) cycloaddition of organic nitriles with NaN3 to afford 5-substituted 1H-tetrazoles in excellent yields. Shorter reaction times, easy work-up, and substantial and pure product formation are the key advantages of the present method.

Fluoroquinolone analogs were synthesized by reductive amination and screened for their antibacterial activities against E. coli K12 and S. aureus RN4220. Out of 18 compounds under the present study, 8 compounds were found most active against S. aureus RN4220 and E. coli K12, respectively, with MIC

Fluoroquinolone analogs were synthesized by simple alkylation followed by click chemistry and evaluated for their antimalarial in vitro against chloroquine sensitive strain of Plasmodium falciparum while ciprofloxacin was used as standard. Our results showed that the compound 12 was found most active with IC50 value of 1.33 μg/mL while ciprofloxacin showed IC50 = 8.81 μg/mL. Therefore, screening of either known or unknown quinolone/fluoroquinolone analogs are worthwhile to find more potent antimalarial drugs which might prove useful in the treatment of mild or severe malaria in human either alone or in combination with existing antimalarial drugs.

Twenty-seven novel chalcone derivatives were synthesized using Claisen-Schmidt condensation and their antimalarial activity against asexual blood stages of Plasmodium falciparum was determined. Antiplasmodial IC50 (half-maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was 1-(4-benzimidazol-1-yl-phenyl)-3-(2, 4-dimethoxy-phenyl)-propen-1-one with IC50 of 1.1 μg/mL, while that of the natural phytochemical, licochalcone A is 1.43 μg/mL. The presence of methoxy groups at position 2 and 4 in chalcone derivatives appeared to be favorable for antimalarial activity as compared to other methoxy-substituted chalcones. Furthermore, 3, 4, 5-trimethoxy groups on chalcone derivative probably cause steric hindrance in binding to the active site of cysteine protease enzyme, explaining the relative lower inhibitory activity.

Environmentally benign ionic liquid [bmim]HSO4 was found suitable for conversion of nitriles into carboxylic acids under mild conditions with excellent purity.

Several new chalcone analogues were synthesized and evaluated as inhibitors of malaria parasite. Inhibitory activity was determined in vitro against a chloroquine-sensitive Plasmodium falciparum strain of parasites. The compound 3-(4-methoxyphenyl)-1-(4-pyrrol-1-yl-phenyl)prop-2-en-1-one was found to be the most active with 50% inhibition concentration (IC50) of 1.61 μg/ml. This inhibitory concentration is comparable to a prototype phytochemical chalcone, licochalcone A, with an IC50 of 1.43 μg/ml. The present study suggests that small, lipophilic nitrogen heterocyclic ring A together with small hydrophobic functionality at ring B can enhance antimalarial activity. These results suggest that chalcones are a class of compounds that provides an option of developing inexpensive, synthetic therapeutic antimalarial agents in the future. Claisen-Schmidt condensation method was employed to synthesize various substituted chalcones. Among all, 3-(4-Methoxyphenyl)-1-(4-pyrrol-1-yl-phenyl)prop-2-en-1-one was found to be most effective with IC50 value of 1.6 μg/ml in vitro against chloroquine sensitive strain (3D7) of Plasmodium falciparum.

A very efficient chiral organocatalyst was prepared from the readily available cyanuric chloride. The asymmetric catalyst exhibited a highly enantioselective catalytic performance for the alkylation of a glycinate Schiff base, which provides a useful procedure for the enantioselective synthesis of structurally diverse natural and unnatural α-alkyl-α-amino acids.

Alkyl, benzyl, aryl, and hetaryl carboxylic acids are successfully coupled with primary aliphatic and aromatic amines as well as secondary aliphatic amines.

The CAN-catalyzed cycloaddition of nitriles with NaN3 is advantageous with regards to short reaction times, easy work up, and high yields.

Peptide nucleic acid (PNA) oligomers were conjugated to cell-penetrating peptides: pAnt, a 17-residue fragment of the Drosophila protein Antennapedia, and pTat, a 14-amino acid fragment of HIV protein Tat. A 14-mer PNA was attached to the peptide by disulfide linkage or by maleimide coupling. The uptake of (directly or indirectly, via biotin) fluorescein-labeled peptides, PNAs, or PNA-peptide conjugates was studied by fluorescence microscopy, confocal laser scanning microscopy, and fluorometry in five cell types. In SK-BR-3, HeLa, and IMR-90 cells, the PNA-peptide conjugates and a T1, backbone-modified PNA were readily taken up (2 microM). The PNA was almost exclusively confined to vesicular compartments in the cytosol. However, the IMR-90 cells also showed a weak diffuse staining of the cytoplasm. In the U937 cells, we observed a very weak and exclusively vesicular staining with the PNA-peptide conjugates and the T(lys)-modified PNA. No evident uptake of the unmodified PNA was seen. In H9 cells, both peptides and the PNA-peptide conjugates quickly associated with the membrane, followed by a weak intracellular staining. A cytotoxic effect resulting in artificial staining of the cells was observed with fluoresceinated peptides and PNA-peptide conjugates at concentrations above 5-10 microM, depending on cell type and incubation time. We conclude that uptake of PNAs in many cell types can be achieved either by conjugating to certain peptides or simply by charging the PNA backbone using lysine PNA units. The uptake is time, temperature, and concentration dependent and mainly endocytotic. Our results also show that proper controls for cytotoxicity should always be carried out to avoid misinterpretation of visual data.

Environmentally benign ionic liquid [bmim]HSO4 was found suitable for conversion of nitriles into carboxylic acids under mild conditions with excellent purity.

Compound 7-(prop-2-yn-1-yloxy)-2H-chromen-2-one was synthesized by Pechmann condensation reaction and characterized by various spectroscopic techniques. The structure of title compound was confirmed by single crystal X-ray diffraction. The compound crystallized in the orthorhombic system with P 21 21 21 space group and the corresponding lattice parameters were found to be a = 4.0138 (11) A, α = 90°; b = 23.536 (6) A, β = 90°; c = 10.93 (2) A, γ = 90°. The crystal packing of molecule showed that intermolecular hydrogen bonds C3–H3⋯O3 [D = 3.53 A], C-13–H13⋯O2 [D = 3.67 A] and intermolecular short interaction between C1–H1⋯C1–H1 [2.68 A] forms a dimeric unit which finally stabilizes the crystal packing in three dimensional network in the molecule. Absorption and emission spectra shows that compound is fluorescent with good Stoke shift values ranging between 57 and 62 nm. Thermal analysis further supports by TGA, DTA. The photophysical results show that the compound exhibits change in fluorescence quantum yield with change in solvent polarity. The structural parameters and the vibrational wave numbers obtained from the optimized geometry of the compound from DFT-B3LYP calculations employing 6-311G (d,p) basis set are in good agreement with the experimental data. UV–Vis spectrum calculated by employing time dependent density functional theory (TD-DFT) is also in very good agreement with the experiment for all solvents.

Antisense peptide nucleic acids (PNAs) can specifically inhibit Escherichia coli gene expression and growth and hold promise as anti-infective agents and as tools for microbial functional genomics. Here we demonstrate that chemical modification improves the potency of standard PNAs. We show that 9- to 12-mer PNAs, especially when attached to the cell wall/membrane-active peptide KFFKFFKFFK, provide improvements in antisense potency in E. coli amounting to two orders of magnitude while retaining target specificity. Peptide-PNA conjugates targeted to ribosomal RNA (rRNA) and to messenger RNA (mRNA) encoding the essential fatty acid biosynthesis protein Acp prevented cell growth. The anti-acpP PNA at 2 microM concentration cured HeLa cell cultures noninvasively infected with E. coli K12 without any apparent toxicity to the human cells. These results indicate that peptides can be used to carry antisense PNA agents into bacteria. Such peptide-PNA conjugates open exciting possibilities for anti-infective drug development and provide new tools for microbial genetics.

Two series of peptides, designated K and NK were synthesized and tested for lipid A binding and neutralizing properties. K2, which has an 11-residue amphiphilic core, and a branched N-terminus bearing two branched lysinyl residues does not bind lipid A, while NK2, also with an 11-residue amphiphilic core comprised entirely of non-ionizable residues, and a similarly branched, cationic N-terminus, binds lipid A very weakly. Both peptides do not inhibit lipopolysaccharide (LPS) activity in the Limulus assay, nor do they inhibit LPS-induced TNF-α and NO production in J774 cells. These results are entirely unlike a homologous peptide with an exclusively hydrophobic core whose LPS-binding and neutralizing properties are very similar to that of polymyxin B [David SA, Awasthi SK, Wiese A et al. Characterization of the interactions of a polycationic, amphiphilic, terminally branched oligopeptide with lipid A and lipopolysaccharide from the deep rough mutant of Salmonella minnesota . J Endotoxin Res 1996; 3: 369—379]. These data suggest that a clear segregation of charged and apolar domains is crucial in molecules designed for purposes of LPS sequestration and that head-tail (polar) orientation of the cationic/hydrophobic regions is preferable to molecules with mixed or facial cationic/amphipathic character.

A synthetic octapeptide, Boc-Leu-Val-Val-D-Pro-Gly-Leu-Val-Val-OMe (1) has been designed as a model for a beta-hairpin conformation. Circular dichroism spectra in various organic solvents reveal a single negative band at 214-217 nm consistent with beta-sheet structures. NMR studies in CDCl3 and C6D6 establish the solvent shielded nature of the Leu(1), Val(3), Leu(6) and Val (8) NH groups. Nuclear Overhauser effects are observed between Val(7) C alpha H and Val(2) C alpha H protons providing strong support for a beta-hairpin conformation. Several important diagnostic interresidue NOEs establish a Type II' beta-turn conformation for the D-Pro-Gly segment and extended conformations for the amino and carboxyl terminal tripeptide arms. The high solubility of the beta-hairpin peptide in organic solvents holds promise for the development of models for three and four stranded beta-sheets.

Twenty-seven novel chalcone derivatives were synthesized using Claisen-Schmidt condensation and their antimalarial activity against asexual blood stages of Plasmodium falciparum was determined. Antiplasmodial IC(50) (half-maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was 1-(4-benzimidazol-1-yl-phenyl)-3-(2, 4-dimethoxy-phenyl)-propen-1-one with IC(50) of 1.1 μg/mL, while that of the natural phytochemical, licochalcone A is 1.43 μg/mL. The presence of methoxy groups at position 2 and 4 in chalcone derivatives appeared to be favorable for antimalarial activity as compared to other methoxy-substituted chalcones. Furthermore, 3, 4, 5-trimethoxy groups on chalcone derivative probably cause steric hindrance in binding to the active site of cysteine protease enzyme, explaining the relative lower inhibitory activity.

A new series of 1, 3-Benzoxazines were synthesized, characterized ((1)H NMR and (13)C NMR) and evaluated for their pesticidal activity. Six new 3-alkyl-3, 4-dihydro-4-methyl-2H-1, 3-benzoxazines (1-6) were prepared by hydroxymethylation of secondary amines with formaldehyde in 65-68% yields. These compounds were screened for there IGR activity against Spodoptera litura and for antifungal fungal activity in vitro against Sclerotium rolfsii ITCC 6181 by poisoned food technique. Insect Growth Regulatory (IGR) activity against Spodoptera litura showed that compound 3-Nonyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines was most effective as IGR with larval GI(50) of 1.863 mu g/Insect. Compounds 3-Octyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines and 3-Decyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines were effective IGRs. Antifungal screening revealed that compound 3-Dodecyl-3, 4-dihydro-4-methyl-2H-1,3-benzoxazines, was highly effective against Sclerotium rolfsii with LC(50) value 31.7 mg L(-1) comparable with commercial fungicide Hexaconazole (LC(50) 1.27 mg L(-1)). Also compounds 3-Nonyl-3, 4-dihydro-4-methyl-2H-1,3-benzoxazines and 3-Decyl-3,4-dihydro-4-methyl-2H-1,3-benzoxazines displayed promising fungitoxicity. The results described in this paper are promising and provides new array of synthetic chemicals to be utilized as pesticides.

An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies.

An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies.

Beta-hairpin structures have been crystallographically characterized only in very short acyclic peptides, in contrast to helices. The structure of the designed beta-hairpin, t-butoxycarbonyl-Leu-Val-Val-D-Pro-Gly-Leu-Val-Val-OMe in crystals is described. The two independent molecules of the octapeptide fold into almost ideal beta-hairpin conformations with the central D-Pro-Gly segment adopting a Type II' beta-turn conformation. The definitive characterization of a beta-hairpin has implications for de novo peptide and protein design, particularly for the development of three- and four-stranded beta-sheets.

Background Emergence of drug-resistant parasite strains has surfaced as a major obstacle in attempts to ameliorate malaria. Current treatment regimen of malaria relies on the concept of artemisinin-based combination therapy (ACT). Methods Fluoroquinolone analogues, compounds 10, 12 and 18 were investigated for their anti-malarial interaction in combination with artemisinin in vitro, against Plasmodium falciparum 3D7 strain, employing fixed-ratio combination isobologram method. In addition, the efficacy of these compounds was evaluated intraperitoneally in BALB/c mice infected with chloroquine-resistant Plasmodium berghei ANKA strain in the Peters’ four-day suppressive test. Results Promising results were obtained in the form of synergistic or additive interactions. Compounds 10 and 12 were found to have highly synergistic interactions with artemisinin. Antiplasmodial effect was further verified by the convincing ED50 values of these compounds, which ranged between 2.31 and 3.09 (mg/kg BW). Conclusions In vivo studies substantiated the potential of the fluoroquinolone derivatives to be developed as synergistic partners for anti-malarial drug combinations.