Current Organic Chemistry - Volume 17, Issue 10, 2013

Synthesis of the functionalized silica-coated magnetic nanoparticles (Si-MNPs) was achieved with organic/inorganic hybrids and approached for high throughput biomolecular separation. To increase the reactivity between biomolecules and Si-MNPs, organic/ inorganic hybrid functionalization has been obtained through the coupling of organosilanes, having various organic residues, with free sianol groups of the silica surfaces. This review gives an overview of the preparation, properties, and current applications of the materials in the areas of immunomagnetic and enzymatic separations as well as biomolecule separations, with the main focus being on Si- MNPs. The organic/inorganic hybrid functionalized Si-MNPs allow the development of sophisticated nanoscale separation systems for bioanalytical, biosensor-based, clinical and environmental applications.

Our aim was to investigate the influence of magnetic nanoparticles of Fe3O4/oleic acid - core/shell on the adherence to cellular and inert substrata of clinical fungal using direct and inverted optic microscopy and Confocal Laser Scanning Microscopy (CLSM). The biofilm development ability varied with the tested species (C. albicans>C. tropicalis>C. glabrata>S. cerevisiae>C. krusei>C. famata), its intensity being correlated with early germ tubes production. The magnetite nanoparticles strongly inhibited the mature biofilms development (of 48 and 72 hours) as well as the fungal adherence to the cellular substratum, suggesting that magnetic nanoparticles could be used for obtaining new materials with anti-adherence properties.

A simple method for the synthesis of magnetic hollow silica microspheres is reported. Magnetic hollow silica was obtained after pretreating via precipitation method of the dextran template microspheres with magnetite. Silica shell was obtained from Na2SiO3. After thermal decomposition of the dextran template, the magnetic silica shells remained intact, as demonstrated by SEM and no evidence of dextran remnants was found according to FT-IR spectra. XRD patterns showed the formation of well-crystallized Fe3O4 and Fe2O3, even if the silica presence can be identified by FT-IR, XRD spectrum do not exhibit the formation of SiO2 network because of the very low degree of cristallinity. This material has been prepared in order to develop a magnetic drug delivery system that can be used to facilitate the targeted drug delivery of antibiotics, by testing the comparative antimicrobial activity of antibiotics themselves as well as loaded into the magnetic hollows against the suspended microbial cells. Citotoxicity studies have been carried on for the new materials by using tripan blue staining technique and eukaryotic cell cycle analysis. The obtained magnetic hollows proved to exhibit low citotoxicity levels on the HCT8 standardized cell line. The antimicrobial susceptibility assay revealed an improvement of the antimicrobial activity of the tested antibiotics on S. aureus, but not on E. coli strain. These results are demonstrating the potential use of the obtained microspheres as biocompatible antibiotic delivery and/or controlled release systems with. However, their efficiency seems to be dependent on the antibiotic structure as well as on the tested microbial strain.

In recent few decades, magnetic nanoparticles have emerged as an ideal support for catalysts because of their easy preparation and functionalization, low toxicity and price. Magnetic nanoparticles-supported catalysts have been used to catalyze lots of organic reactions, including C-C bond form reaction, hydrogenation reaction, oxidation reaction, phase-transfer reaction and dihydroxylation reaction. They can be recovered easily by an external magnet and reused several times with sustained activities. In this review, the application of magnetite nanoparticles-supported organic small molecule or biocatalyst in organic reactions will be summarized.

A novel Pd(II) organometallic catalyst bonded to magnetic SiO2@Fe3O4 support was synthesized by coordinating Pd(II) with the PPh2-ligand originally grafted onto the silica layer covering the Fe3O4 microspheres. Owing to the high dispersion of Pd(II) active sites, the as-prepared Pd-PPh2-SiO2@Fe3O4 catalyst exhibited comparable activities and selectivities with the PdCl2(PPh3)2 homogeneous catalyst in various water-medium Suzuki and Sonogashira reactions. The catalyst could be easily recycled by an external magnet and used repetitively for at least 8 times without significant loss of its catalytic activity.

The adaptation of marine organisms to a wide range of environmental conditions in the specific environment (temperature, salinity, tides, pressure, radiation, light, etc.) has made them an enormous reservoir of interesting biological material for both basic research and biotechnological improvements. Both this evolutionary richness and the knowledge of enzyme action including the comprehension of interactive effects of the environmental factors, are of key importance to exploit biocatalyst's potential. But above all a marine enzyme may carry novel chemical and stereochemical properties thus biocatalytically oriented studies (testing of suitable substrates, appropriate checking of reaction conditions, study of stereochemical asset of catalysis) should be performed to appropriately reveal this “chemical biodiversity”. In this review article, comparing among enzymes from terrestrial and marine environments, ten cases in point will be depicted after general considerations on marine organisms and marine biocatalysts. Each case has been selected for its importance related to the field of biocatalysis, showing practical details to value the concept of potential usefulness of marine enzymes for organic chemists. From this analysis a foresight regarding the strategic potential of marine habitat resulted clear. Sustainability of collection methods and availability of commercial fresh organisms are two important aspects, also in relation to international policy on biodiversity. As early as scientific interest arise, possibly the way to access useful biocatalysts should avoid destructive large-scale collections of marine biomass, then recombinant biocatalysts become desirable and should be possible after gene identification.

The present review deals with the C-prenylation of phenolic compounds, the topic has even gained a considerable scientific attention but still poorly described in the literature. A brief introduction on natural sources of C-prenylated phenolics is highlighted in the first lines, underlining also few of the recent studies on identification, biological applications and biosynthesis of mainly C-prenylflavonoids and -xanthones along with other small C-prenylated phenolic molecules. The paper is majorly focusing on the organic synthetic aspects, throughout, a hundred of papers are reviewed since 1970; most of them have been published during the last decade. A chronological dialogue is presented in order to find out the research progress on the synthesis of this important class of natural compounds; a quite number of synthetic products show higher biological impact than the natural models.

The synthesis and characterization of the first rigid fused porphyrin-phthalocyanine hetero-dyad with two different metals is reported; was based on porphyrin's dienophile features in Diels-Alder reactions. This synthetic procedure represents a new approach for the synthesis of extended systems based on tetrapyrrolic macrocycles.

Catalytic amounts of NaNO2 are able to successfully promote the reaction between 1,4-hydroquinone and methanol under acidic conditions, affording selectively the corresponding mequinol in excellent isolated yields. According to the proposed reaction mechanism, the semi-quinone intermediate, generated in situ from the corresponding hydroquinone by NO2 oxidation, is the real reactive species, undergoing nucleophilic attack onto the alcoholic molecule. Experimental evidences emphasize the key role of NO2. After optimization of the reaction conditions, the scope of the proposed protocol is extended to a wider range of alcohols, providing the corresponding mono-ethers in good to excellent yields. Moreover, when substituted hydroquinones are selected as reactive substrates, monoetherification occurs with complete regio-selectivity towards the less hindered phenolic -OH group.

The synthesis of novel acyclic pyrimidine nucleoside analogues with 1,2,3-triazole ring bound via ethylene spacer or directly to C-5 of pyrimidine ring has been reported. 1,4-Disubstituted 1,2,3-triazoles were synthesized by click chemistry approach using regioselective copper(I)-catalyzed 1,3-dipolar cycloaddition reaction between terminal alkyne and azido pyrimidines under both conventional (method A) and microwave (method B) conditions. N-Alkylation of triazolyl pyrimidines afforded 5-[2-(1,2,3- triazolyl)ethyl]pyrimidine derivatives with penciclovir-, ganciclovir-like and 2,3-dihydroxypropyl side chain, as well as 5-(1,2,3- triazolyl)pyrimidine derivatives with penciclovir- and ganciclovir-like side chain. The stereostructures of 2-hydroxyethyl, 2- tosyloxyethyl, 2-azidoethyl and 4-acetoxymethyl-1,2,3-triazolyl C-5 substituted pyrimidine derivatives were unambiguously confirmed by their X-ray crystal structure analysis.

Following our previous studies, to affiliate selective pharmacophore in a single molecular entity, domino, ecologically benign, four hetero-component, single pot reaction has been carried out in (bmim)BF4 ionic liquid to structure a new class of compact heteronuclei. In a newly constructed heterocyclic Ugi adducts, quinoline was used as nitrogen source and benzothiazole as well as thiophene moieties were selected to introduce sulphur functionality. This Ugi eco-compatible heterocyclic synthesis resulted in relatively good yields with prompt reaction time. New products were screened for their in vitro antimicrobial activity against a representative panel of bacteria and fungi and some of the final analogues displayed more or equal potency at MIC range 6.25-25 µg/mL than control drugs ampicillin, gentamicin and fluconazole (MICs: 6.25-25 µg/mL). The structural assignments of the new products were done on the basis of FT-IR, 1H NMR spectroscopy and elemental analysis.