Ruthenium(II) Arene Complexes Bearing Simple Dioxime Ligands: Effective Catalysts for the One-Pot Transfer Hydrogenation/N-Methylation of Nitroarenes with Methanol

The reductive N-monomethylation of nitroarenes is a reaction of wide scientific interest that can be conveniently realized in one-pot using methanol as both the reductant (H2 donor), alkylating agent (CH3+...

Synthesis of hydrophilic carbon nanotube sponge via post-growth thermal treatment

Clean water is vital for healthy ecosystems, for human life and, in a broader sense, it is directly linked to our socio-economic development. Nevertheless, climate change, pollution and increasing world population will likely make clean water scarcer in the near future. Consequently, it becomes imperative to develop novel materials and more efficient ways of treating waste and contaminated water. Carbon nanotube (CNT) sponges, for example, are excellent in removing oleophilic contaminants; however, due to their super-hydrophobic nature, they are not as efficient when it comes to absorbing water-soluble substances. Here, by means of a scalable method consisting of simply treating CNT sponges at mild temperatures in air, we attach oxygen-containing functional groups to the CNT surface. The functionalized sponge becomes hydrophilic while preserving its micro- and macro-structure and can therefore be used to successfully remove toxic contaminants, such as pesticides, that are dissolved in water. This discovery expands the current range of applications of CNT sponges to those fields in which a hydrophilic character of the sponge is more suitable.

Support-Activity Relationship in Heterogeneous Catalysis for Biomass Valorization and Fine-Chemicals Production

Heterogeneous catalysts are progressively expanding their field of application, from high-throughput reactions for traditional industrial chemistry with production volumes reaching millions of tons per year, a sector in which they are key players, to more niche applications for the production of fine chemicals. These novel applications require a progressive utilization reduction of fossil feedstocks, in favor of renewable ones. Biomasses are the most accessible source of organic precursors, having as advantage their low cost and even distribution across the globe. Unfortunately, they are intrinsically inhomogeneous in nature and their efficient exploitation requires novel catalysts. In this process, an accurate design of the active phase performing the reaction is important; nevertheless, we are often neglecting the importance of the support in guaranteeing stable performances and improving catalytic activity. This review has the goal of gathering and highlighting the cases in which the supports (either derived or not from biomass wastes) share the worth of performing the catalysis with the active phase, for those reactions involving the synthesis of fine chemicals starting from biomasses as feedstocks.

Green and Scalable Preparation of Colloidal Suspension of Lignin Nanoparticles and Its Application in Eco-friendly Sunscreen Formulations

Lignin nanoparticles (LNPs) are applied in several industrial applications. The nanoprecipitation of LNPs is fast and inexpensive but currently still limited to the use of hazardous organic solvents, making it difficult to apply them on a large scale. Here, we report a scalable nanoprecipitation procedure for the preparation of colloidal lignin nanoparticles (cLNPs) by the use of the green solvents dimethylisosorbide and isopropylidene glycerol. Irrespective of the experimental conditions, cLNPs showed higher UV absorbing properties and radical scavenging activity than parent LNPs and raw lignin. cLNPs were successively used in the preparation of eco-friendly sunscreen formulations (SPF 15, 30, and 50+, as evaluated by the COLIPA assay), which showed high UV-shielding activity even in the absence of synthetic boosters (microplastics) and physical filters (TiO2 and ZnO). Biological assays on human HaCaT keratinocytes and human skin equivalents demonstrated the absence of cytotoxicity and genotoxicity, associated with an optimal protection of the skin from UV-A damage.

On the Capability of Oxidovanadium(IV) Derivatives to Act as All-Around Catalytic Promoters Since the Prebiotic World

For a long time the biological role of vanadium was not known, while now the possibility of using its derivatives as potential therapeutic agents has given rise to investigations on their probable side effects. Vanadium compounds may inhibit different biochemical processes and lead to a variety of toxic effects and serious diseases. But, on the other hand, vanadium is an essential element for life. In recent years, increasing evidence has been acquired on the possible roles of vanadium in the higher forms of life. Despite several biochemical and physiological functions that have been suggested for vanadium and notwithstanding the amount of the knowledge so far accumulated, it still does not have a clearly defined role in the higher forms of life. What functions could vanadium or its very stable oxidovanadium(IV) derivatives have had in the prebiotic world and in the origins of life? In this review, we have briefly tried to highlight the most useful aspects that can be taken into consideration to give an answer to this still unresolved question and to show the high versatility of the oxidovanadium(IV) group to act as promoter of several oxidation reactions when coordinated with a variety of ligands, including diketones like acylpyrazolones.

Dendrimer crown-ether tethered multi-wall carbon nanotubes support methyltrioxorhenium in the selective oxidation of olefins to epoxides

Benzo-15-crown-5 ether supported on multi-wall carbon nanotubes (MWCNTs) by tethered poly(amidoamine) (PAMAM) dendrimers efficiently coordinated methyltrioxorhenium in the selective oxidation of olefins to epoxides.

Layer by layer supported laccase on lignin nanoparticles catalyzes the selective oxidation of alcohols to aldehydes

Lignin nanoparticles support laccase from Trametes versicolor in the selective oxidation of alcohols to aldehydes, in the presence of redox mediators.

Iodoxybenzoic Acid Supported on Multi Walled Carbon Nanotubes as Biomimetic Environmental Friendly Oxidative Systems for the Oxidation of Alcohols to Aldehydes

Iodoxybenzoic acid (IBX) supported multi walled carbon nanotube (MWCNT) derivatives have been prepared as easily recyclable solid reagents. These compounds have been shown to be able to mimic the alcohol dehydrogenases and monooxygenases promoted oxidation of aromatic alcohols to corresponding aldehydes. Their reactivity was found to be dependent on the degree of functionalization of MWCNTs as well as from the chemical properties of the spacers used to bind IBX on the surface of the support. Au-decorated MWCNTs and the presence of longer spacers resulted in the optimal experimental conditions. A high conversion of the substrates and yield of desired products were obtained.

Advances in biotechnological synthetic applications of carbon nanostructured systems

In the last few years carbon nanostructures have been applied for the immobilization of enzymes and biomimetic organo-metallic species useful for biotechnological applications. The nature of the support and the method of immobilization are responsible for the stability, reactivity and selectivity of the system. In this review, we focus on the recent advances in the use of carbon nanostructures, carbon nanotubes, carbon nanorods, fullerene and graphene for the preparation of biocatalytic and biomimetic systems and for their application in the development of green chemical processes.

Double hydrophosphination of alkynes promoted by rhodium: the key role of an N-heterocyclic carbene ligand

The stereoelectronic properties of the NHC ligand make possible the rhodium-catalysed double hydrophosphination of alkynes avoiding the catalyst deactivation by the diphosphine product.

Synthesis of 2'-deoxy-1'-homo-N-nucleosides with anti-influenza activity by catalytic methyltrioxorhenium (MTO)/H2O2 oxyfunctionalization

This paper describes a new route for the synthesis of 1'-homo-N-nucleoside derivatives by means of either methyltrioxorhenium (MTO) or supported MTO catalysts, with H(2)O(2) as the primary oxidant. Under these selective conditions, the oxyfunctionalization of the heterocyclic ring and the N heteroatom oxidation were operative processes, regardless of the type of substrate used, that is, purine or pyrimidine derivatives. In addition, the oxidation of 1'-homo-N-thionucleosides, showed the occurrence of site-specific oxidative nucleophilic substitutions of the heterocyclic ring. The MTO/H(2)O(2) system showed, in general, high reactivity under both homogeneous and heterogeneous conditions, affording the final products with high conversion values of substrates and from medium to high yields. Many of the novel 1'-homo-N-nucleoside analogues were active against the influenza A virus, without any cytotoxic effects, retaining their activity in both protected and unprotected forms.

Advances in the synthesis of bioactive unnatural amino acids and peptides

The key role of proteins and amino acids in the structure and function of living matter has stimulated extensive studies. Modified amino acids with enhanced biological activity, proteolitic stability and bioavailability are of increasing interest in protein design and engineering as drug candidates. In the last few years, several efforts have been devoted to the synthesis of amino acids having unusual side chains and unnatural chirality, commonly referred to as "nonproteinogenic" or "unnatural" amino acids, even though some of them can be isolated from natural sources. In this review we describe recent advances in the amino acid side-chain transformations and backbone modifications by oxidative and fluorination procedures.

Exploring the frontiers of synthetic eumelanin polymers by high-resolution matrix-assisted laser/desorption ionization mass spectrometry

New trends in material science and nanotechnologies have spurred growing interest in eumelanins black insoluble biopolymers derived by tyrosinase-catalysed oxidation of tyrosine via 5,6-dihydroxyindole (DHI) and its 2-carboxylic acid (DHICA). Efficient antioxidant and photoprotective actions, associated with peculiar optoelectronic properties, are recognised as prominent functions of eumelanin macromolecules within the human and mammalian pigmentary system, making them unique candidates for the realisation of innovative bio-inspired functional soft materials, with structure-based physical-chemical properties. An unprecedented breakthrough into the mechanism of synthetic eumelanin buildup has derived from a detailed investigation of the oxidative polymerization of DHI and its N-methyl derivative (NMDHI) by linear and reflectron matrix-assisted laser/desorption ionization mass spectrometry. Regular collections of oligomers of increasing masses, spanning the entire m/z ranges up to 5000 Da (>30-mer) and 8000 Da (> 50-mer) for the two building blocks, respectively, were disclosed. It is the first time that the in vitro polymerisation of dihydroxyindoles to form synthetic eumelanins is explored up to its high mass limits, giving at the same time information on the polymerisation mode, whether it follows a stepwise pattern (being this the conclusion in our case) or a staking sequencing of small-sized entities. It also highlighted the influence of the N-methyl substituent on the polymerization process; this opens the way to the production of N-functionalized, synthetic eumelanin-inspired soft materials, for possible future technological applications.

Methyltrioxorhenium catalysis in nonconventional solvents: a great catalyst in a safe reaction medium

The requirement that chemical processes are sustainable, reflected in waste reduction and the use of safe reagents and reaction conditions, is becoming even more stringent as a result of pressure by society and governments to preserve the environment and protect human health. Catalysis offers numerous benefits related to green chemistry, including lowered energetic reaction requirements; catalytic, rather than stoichiometric, amounts of materials; increased selectivity; lowered consumption of processing and separation agents; and, in many cases, the use of less-toxic compounds. Our research group has for a long time been studying methyltrioxorhenium in the oxyfunctionalization of different substrates, by using H(2)O(2) or its urea-hydrogen peroxide complex as the primary oxidant. In this Review paper we aim to provide a full literature account on the catalytic activity and selectivity of methyltrioxorhenium in the oxyfunctionalization reaction, either in nonconventional solvents or under solvent-free conditions, with a particular emphasis on the use of ionic liquids as green reaction media.

Platinum-Based Antitumor Drugs Containing Enantiomerically Pure α-Trifluoromethyl Alanine as Ligand

Synthetic amino acids such as fluorinated alpha-amino acids are currently actively investigated for their biological activity. Herein, we report on the synthesis and characterization of platinum complexes containing an N,O-chelated pure enantiomer of alpha-trifluoromethylalanine (alpha-Tfm-Ala). The compounds are either anionic, K[PtCl2(alpha-Tfm-Ala)], or cationic, [PtAm2(alpha-Tfm-Ala)](NO3) (Am2= (NH3)2, ethylendiamine (en), 1,10-phenanthroline (phen), and 2,9-dimethyl-1,10-phenanthroline (Me2phen)). All complexes are highly soluble in water and have been fully characterized by NMR spectroscopy. In vitro cytotoxicity assays on different human tumor cell lines have been performed on some of the isolated compounds. [Pt(NH3)2(alpha-Tfm-Ala)] with R configuration of the amino acid proved to have an activity comparable to that of the reference compound cisplatin. Flow cytometric analysis on NCI-H460 tumor cells (absence of G2/M arrest, which instead is observed in the case of cisplatin) suggests a mechanism of action different from that of cisplatin.

Design, modelling, synthesis and biological evaluation of peptidomimetic phosphinates as inhibitors of matrix metalloproteinases MMP-2 and MMP-8

Three novel peptidomimetic phosphinate inhibitors have been synthesized and evaluated as inhibitors of matrix metalloproteinases MMP-2 and MMP-8. Their IC50 values are in the micromolar range, and one of them showed to be the most effective inhibitor of MMP-2. The differences in binding affinities for MMP-2 and MMP-8 of the three phosphinates have been rationalized by means of modelling studies and molecular dynamics simulations.

Synthesis and evaluation of new tripeptide phosphonate inhibitors of MMP-8 and MMP-2

The phosphotryptophan derivative l-Pro-l-Leu-l-(P)Trp(OH)(2) (2b) was reported as the first example of left-hand-sideLeft-hand-side inhibitors: inhibitors that bind in the unprime region of the enzyme active site, in reference to the convention of drawing the unprimed residues of a peptide substrate on the left side. [R.P. Beckett et al., Drug Discov. Today 1 (1996) 16-26]. The opposite applies to right-hand-side inhibitors. phosphonate inhibitor of MMP-8. Its uncommon mode of binding to MMP-8 was mainly ascribed to the presence of the proline residue in P(3). Ten new analogues of 2b were obtained by replacement of the aminoterminal l-Pro with aminoacid residues bearing small side chains. Most of the new analogues show an increase of affinity for MMP-2 and MMP-8, and different profiles of selectivity. Computer simulations were performed to explain the effects of substitutions on the preferred mode of binding. They reveal that most of the new analogues are probably accommodated in the right, rather than left-hand side of MMP-8 active site.

Enantioseparation of amino acid derivatives by capillary zone electrophoresis using vancomycin as chiral selector

The separation of racemic derivatized amino acids (N-acetyl) into their enantiomers was achieved using capillary zone electrophoresis employing vancomycin as a chiral selector. Due to the strong absorption properties of the chiral selector at the low wavelengths used, the partial-filling countercurrent method was adopted in order to improve method sensitivity. In the separation system studied, the chiral selector filled only a part of the capillary and, due to the appropriate selection of the pH, was moving in the opposite direction of the analytes keeping the detector free from absorbing compounds. The effect of several experimental parameters on the enantioresolution of analytes was studied, e.g., vancomycin concentration (0-5 mM), pH of the background electrolyte (pH 4-7), capillary temperature (15-35 degrees C), and the presence of an organic modifier in the run buffer (methanol or ethanol or n-propanol). N-Acetyl glutamic acid, serine, cystine, tyrosine, and proline were all baseline-resolved into their enantiomers and the enantioresolution factor (R(s)) was increased by raising the vancomycin concentration. pH 4 allowed the baseline resolution of the five studied analytes in the presence of 2.5 mM of chiral selector and an increase in pH caused a decrease of R(s).

First synthesis of totally orthogonal protected alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines

The first synthesis of a series of totally orthogonal protected racemic alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines is described. The key steps of the synthesis are the mild guanidinylation procedure and the selective hydrogenation of a CC triple bond in the presence of a Cbz-group.