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Peptide hydrolysis has been involved in a wide range of biological, biotechnological, and industrial applications. In this perspective, the mechanisms of three distinct peptide bond cleaving enzymes, beta secretase (BACE1), insulin degrading enzyme (IDE), and bovine lens leucine aminopeptidase (BILAP), have been discussed. BACE1 is a catalytic Asp dyad [Asp, Asp−] containing aspartyl protease, while IDE and BILAP are mononuclear [Zn(His, His, Glu)] and binuclear [Zn1(Asp, Glu, Asp)–Zn2(Lys, Glu, Asp, Asp)] core possessing metallopeptidases, respectively. Specifically, enzyme–substrate interactions and the roles of metal ion(s), the ligand environment, second coordination shell residues, and the protein environment in the functioning of these enzymes have been elucidated. This information will be useful to design small inhibitors, activators, and synthetic analogues of these enzymes for biomedical, biotechnological, and industrial applications.

A new modified van Leusen strategy has been developed for the synthesis of biologically significant 5-substituted oxazoles by the reaction of (het)aryl methyl alcohols or benzyl bromides as precursors with tosylmethylisocyanide (TosMIC) under basic conditions. This method is efficient, takes place under mild reaction conditions, and is tolerant of various functional groups with high yield.

Gold-catalyzed, regioselective cycloisomerization of N-(o-alkynylaryl)-N-vinyl sulfonamides afforded high yields of 2-sulfonylmethyl-1-benzoazepine derivatives. This 7-endo-dig selective cyclization proceeds via the incorporation of an exocyclic double bond by a labile 1-benzoazepine intermediate. The cyclization substrates were assembled in two steps from readily available materials using Sonogashira coupling and a Cs2CO3-mediated formal vinylic substitution.

Here, we review the advances in understanding the structure and properties of magnetoelectric gallium ferrite (GaFeO3 or GFO). Special significance of GFO lies in its compositional tunability over a large range of Ga:Fe ratio without forming a second phase which also renders prospective room temperature magnetoelectricity in the material. Detailed structural studies show noncentrosymmetric orthorhombic Pc21n symmetry without any structural phase transition between 4 K and 700 K. The material shows a ferrimagnetic behavior driven by cation site disorder, corroborated both experimentally as well as theoretically, with transition temperature dependent upon Ga:Fe ratio. GFO exhibits magnetostructural and magnetoelectric coupling indicating coupling among the structural, magnetic and electrical degrees of freedom which could possibly be utilized to strain engineer electrical and magnetic properties in the thin film structures. However, the biggest challenge remains to reduce the leakage in the material in both...

Regioselective synthesis of 4-hydroxybiphenyl-2-carboxylates via the base-mediated oxygenative [3 + 3] benzannulation reaction of α,β-unsaturated aldehydes and γ-phosphonyl crotonates is reported. A hydroxyl group is installed in the final product on the originally phosphorus-bound carbon via a novel oxygenative and dehydrogenative transformation. The reaction proceeds rapidly in an open flask, uses atmospheric oxygen as an oxidant, and affords good yields of substituted biaryl phenols.

Direct aerobic oxidative cross-dehydrogenative coupling of aryl acetaldehydes at C-3 position of imidazoheterocycles via copper catalyzed reaction resulted in the synthesis of dicarbonylated imidazoheterocycles in 55–85% yields. The methodology provides a straightforward, high yielding and one-pot approach towards the synthesis of C-3 dicarbonylated imidazoheterocycles without prior activation of C(sp2)-H or a base. This also reports the first method of coupling of aryl acetaldehydes on imidazo[1,2-a]pyridine system via double-oxidative cross-dehydogenative process.

The challenge associated with cellulosic ethanol production is maximizing sugar yield at low cost. Current research is being focused to develop a pretreatment method to overcome biomass recalcitrance in an efficient way. This review is focused on two major pretreatments: dilute acid (DA) and ammonia fiber explosion (AFEX) pretreatment of corn stover and how these pretreatment cause morphological and chemical changes to corn stover in order to overcome the biomass recalcitrance. This review highlights the key differences of these two pretreatments based on compositional analysis, cellulose and its crystallinity, morphological changes, structural changes to lignin, enzymatic reactivity and enzyme adsorption onto pretreated solids and finally cellulosic ethanol production from the hydrolysate of DA and AFEX treated corn stover. Each stage of the process, AFEX pretreated corn stover was superior to DA treated corn stover.

The cesium carbonate-mediated reaction of 2-bromoallyl sulfones and ortho-hydroxychalcones furnished 3-arylsulfonyl-4H-chromene derivatives in 58-67% yield (18 examples). 2-Bromoallyl sulfones functioned as synthetic surrogates for allenyl sulfones in the reaction.

A transition metal-free, vinylic bromide displacement reaction of bromoallyl sulfones (II) with phenolate nucleophiles is reported.

The use of NHCs for generating homoenolate species has gained widespread popularity in recent years. A number of highly stereoselective processes of NHC-homoenolates have emerged. Homoenolate reactions have also been employed as key steps in the total synthesis of a number of natural products. The use of compatible co-catalysts, improved NHC-catalyst design and the use of novel precursors for homoenolate generation are among the major developments in this area that were disclosed recently. This tutorial review organises and presents the advancements in this rapidly growing area of catalysis and in the process updates a previous account published in 2011 in this journal.

An efficient method for the synthesis of the title compounds (V) is developed using a microwave-assisted Hinsberg heterocyclization using either montmorillonite or Yb(OTf)3 as catalysts.

According to the title reaction, 4-sulfonylcrotonates or 1,3-bissulfonylpropene are transformed with α,β-unsaturated aryl aldehydes, citronellal, or ketones to form highly substituted 3-sulfonyl benzoic ester derivatives.

Dyes are an important class of organic pollutants and are well known for their hazardous effects on aquatic life in general and human beings in particular. In order to reduce the negative effects of dye contaminated wastewater on humans and the environment, the wastewater must be treated carefully before discharge into main streams. Advances in science and technology have led to the evolution of several techniques for the removal of dyes from industrial and domestic effluents. In this review, the more recent methods for the removal of dyes from water and wastewater have been discussed. Wastewater treatment techniques such as adsorption, oxidation, flocculation–coagulation, membrane filtration and biological treatment have been highlighted. In addition, efforts were made to review all the available techniques and recently published studies from 2010–2014. Furthermore, the performance and special features of these technologies have been summarised. Advantages and limitations of each technique are also presented. A thorough literature survey revealed that chemical oxidation, adsorption, and biological treatments have been the most frequently investigated techniques for dye removal over the past few years.

Base-mediated cyclocondensation of 2-hydroxybenzaldehydes with 3-bromo-1-(arylsulfonyl)propenes and 4-bromocrotonates afforded (E)-2-(2-sulfonylvinyl)benzofurans and (E)-2-benzofuranyl-3-acrylates respectively.

A convenient, two-step synthesis of substituted furans from readily available aryl alkynes and ketones is reported. The furan-forming oxidative cyclization is mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide and can be carried out in an open flask.

Electrophilic iodocyclization of 2-(aminobutyne)-anilines (I) affords selectively pyrrole derivatives (II) rather than alternative indoles.

A Cu-catalyzed tandem approach for the synthesis of indolo- and pyrrolonaphthyridines via regioselective addition of indoles or pyrrole to 3-bromo-2-ethynylpyridines (II) followed by intramolecular cyclization is presented.

Monoalkylation of primary amines using amine hydrobromides and alkyl bromides has been carried out. Under controlled reaction conditions the reactant primary amine was selectively deprotonated and made available for reaction, while the newly generated secondary amine remained protonated, and did not participate in alkylation further. Reaction was carried out under mild reaction conditions and was applicable to a wide range of primary amines and alkyl bromides.

Fe-Ni nanoparticles are used as catalyst for the selective hydrogenation of nitroarenes (I) to anilines (II) as well as cinnamic ester (III) to 3-phenylpropanoate (IV).

The photochemical properties of the compounds (VIIIa), (XII), and (XIII) are investigated in chloroform indicating potential for application as OLEDs.

The synthesis of heterobimetallic complexes is reported and their catalytic activity for the oxidation of hindered phenols as well as the coupling of terminal alkynes to diynes is demonstrated.

The use of microwave energy in chemical reactions has revolutionized the field of heterocyclic chemistry in the past two decades. Synergy of microwave methodology with reactions performed on support media and/or in the absence of solvent constitutes an environmentally clean technique, which offers tremendous advantages such as clean chemistry, reduction in reaction times, improved yields, and applicability to wide range of reactions, safety and tremendous scope for automation over the traditional heating. The benzoannulated azaheterocycles display an impressive repertoire of biological activities. The present review will provide an in-depth view of microwave-assisted preparation of benzo-fused seven- membered azaheterocycles such as benzodiazepines, benzothiazepines and benzoxazepines.

A low-level palladium perovskite catalyst deposited on cerium oxide is efficiently employed for Pd-catalyzed Sonogashira and Heck cross-coupling reactions under continuous flow conditions.

A mechanistically unprecedented approach for the formation of tertiary amides from N,N-dialkylchlorothiophosphoramidates and aldehydes has been developed. The reaction occurred via the activation of aldehydes with N,N-dialkylchlorothiophosphoramidates followed by amidation with dialkylamine pendent of the same phosphoramidate.

Recent years have seen a surge of interest in supramolecular architectures with the focus shifting towards generating discrete molecular assemblies and factors controlling their formation. Such molecular assemblies offer a wide range of applications which are often architecture-dependent. To construct such assemblies, nitrogen-donor ligands have been intensively employed to generate an assorted variety of topologies. Out of various nitrogen-donor ligands, pyridine-amide based ligands stand out as they not only offer structural flexibility and their ability to adjust to the geometrical requirements of a metal ion but also offer dual functional groups: pyridine and amide. The present perspective will focus on recent developments in the design of discrete supramolecular assemblies utilizing pyridine-amide based ligands with a specific stress on the architectural aspects and subsequent applications of designed molecular assemblies.

Emergence of resistance by bacterial and fungal stains towards existing antimicrobial agents is one of the major problem as well as motivation to synthesize a new class of antimicrobial agents possessing potent activity compared to commonly used therapy. Coumarin is the heterocyclic compound formed from benzene and pyrone ring containing oxygen and its derivatives are of wide awareness because of their diverse biological activity and clinical applications, they are remarkably effective compounds both with respect to their inhibitory activity and their favourable selectivity ratio. Coumarins are regarded as a promising class of bioactive heterocyclic compounds that exhibit a range of biological activities like anti-microbial, anti-viral, anti-diabetic, anti-cancer activity, anti-oxidant, anti-parasitic, anti-helmintic, anti-proliferative, anti-convulsant, anti-inflammatory and anti-hypertensive activities etc. The information given in this manuscript may be helpful in the further research of better antimicrobial agents having lesser microbial resistance and improved antimicrobial profile.

An operationally simple approach for the stereoselective tandem synthesis of novel thiazolo fused naphthyridines 5a–o and thienopyridines 8a–e by the reaction of o-alkynylaldehydes with L-cystine methyl ester hydrochloride via Au(III)-catalyzed regioselective 6-endo-dig ring closure under mild reaction conditions is described. It is noteworthy that alkynes bearing an alkyl and a strong electron-withdrawing nitro group successfully afforded the desired products in good yields.

An efficient tandem approach for the regio- and stereoselective synthesis of oxazolo-fused naphthyridines 3a–g, 3i–l and isoquinolines 3h, 3m via the reaction of o-alkynylaldehydes 1a–i with chiral amino alcohols 2a–c under mild reaction conditions is described. The stereochemistry and structures of the products were assigned via NOESY and X-ray crystallographic studies.

The presence of electron donating alkyl groups in starting material (I) is key to the success of the reaction.

Designed materials offer noteworthy applications which are often architecture dependent. Despite knowing such a fact, one of the major challenges faced by the scientific community is to find ways to predict and, if possible, control the resultant architecture of a network. If such an exercise is fruitful, it creates enormous opportunities to synthesize exotic materials with tailor-made applications. Any network is composed of individual molecules and the transition from a single molecule to a network can be achieved through several routes taking advantage of synthetic chemistry. There exists a molecular building block at the heart of such a transition which mediates such a process from a single molecule to a network. Although a large number of building blocks have created assorted materials, utilization of a well-defined coordination complex as the building block (i.e., metalloligand) is unique for the construction of a designed architecture. A coordination complex as the building block offers structural rigidity that places the auxiliary functional groups to a pre-organized conformation. Such auxiliary functional groups could then coordinate a secondary metal ion or be involved in the self-assembly via weak interactions, such as hydrogen bonds. This review focuses on the recent progress achieved through assorted molecular building blocks towards generating ordered networks. Broadly, two classes of metalloligands will be discussed: those offering hydrogen bond sensitive functional groups and those tendering coordination bond responsive groups. Nevertheless, the result is the construction of networks of a highly-ordered nature in both cases. The present review is expected to provide new strategies for constructing functional materials through metalloligands for challenging and practical applications.

Unsymmetrical internal alkynes such as (X) or (XII) generate selectively a single isomers [cf.(XI) or (XIII)].

An efficient approach for the copper-catalyzed regioselective tandem synthesis of diversely substituted indolo[2,1-a]isoquinolines 11a–r, pyrrolo[2,1-a]isoquinolines 12a–d, and indolo-, pyrrolo[2,1-f][1,6]naphthyridines 14a–f via preferential addition of the heterocyclic amines onto the ortho-haloarylalkynes over N-arylation followed by intramolecular C-2 arylation is described. The scope of the developed chemistry was successfully extended for the direct synthesis of bisindolo-, pyrrolo[2,1-a]isoquinolines 15a–g, a regioisomer of the bisindolo[1,2-a]quinolines used as organic single-crystal field-effect transistor. Hydroxymethyl benzotriazole, which is an inexpensive and air stable compound, has been used as a ligand to carry out this one-step conversion of simple, readily available starting materials into an interesting class of heterocyclic compounds.