At the advent of cross-coupling chemistry, carbon electrophiles based on halides or pseudohalides were the only suitable electrophilic coupling partners. Almost two decades passed before the first ...cross-coupling reaction of heteroatom-based electrophiles was reported. Early work by Murai and Tanaka initiated investigations into silicon electrophiles. Narasaka and Johnson pioneered the way in the use of nitrogen electrophiles, while Suginome began the exploration of boron electrophiles. The chemistry reviewed within provides perspective on the use of heteroatomic electrophiles, specifically silicon-, nitrogen-, boron-, oxygen-, and phosphorus-based electrophiles in transition-metal catalyzed cross-coupling. For the purposes of this review, a loose definition of cross-coupling is utilized; all reactions minimally proceed via an oxidative addition event. Although not cross-coupling in a traditional sense, we have also included catalyzed reactions that join a heteroatomic electrophile with an in situ generated nucleophile. However, for brevity, those involving hydroamination or C–H activation as a key step are largely excluded. This work includes primary references published up to and including October 2018.
The possibilities of producing large batches of magnetic nanoparticles (MNPs) using electrical explocion of the wire (EEW), laser target evaporation, and spark discharge are considered. MNP ...bioapplications require production of magnetic materials in the form of as stabilized aqueous suspensions or hydrogels with magnetic fillers; therefore, some details of synthesis of these materials and their certification are discussed. The problems of the interaction of MNPs with biological systems, biocompatibility, the applicability of ferrogel substrata to cellular technology and regenerative medicine, and as biomimetics in the development of magnetic biosensors are considered. The results of analysis of some biological experiments with various suspensions prepared based on the same MNP batch are presented. An analysis of the examples of magnetic biodetection and existing theoretical approaches will allow estimation of prospects of this scientific direction to develop highly sensitive film sensors based on the giant magnetic impedance effect for biomedical applications.
For the first time, an aza‐Heck cyclization that allows the preparation of indoline scaffolds is described. Using N‐hydroxy anilines as electrophiles, which can be easily accessed from the ...corresponding nitroarenes, this method provides indolines bearing pendant functionality and complex ring topologies. Synthesis of challenging indolines, such as those bearing fully substituted carbon atoms at C2, is also possible using this method.
An aza‐Heck cyclization that allows the preparation of indoline scaffolds is described. Using N‐hydroxyanilines as electrophiles, which can be easily accessed from the corresponding nitroarenes, this method provides indolines bearing pendant functionality and complex ring topologies.
The first total synthesis of the natural product impatien A is described. This concise synthesis features an aza-Heck cyclization to construct the complex spirocyclic ring system and provides a rare ...example of the use of aza-Heck cyclizations in complex molecule synthesis. To enable this key cyclization of an electrophilic nitrogen atom with a tetrasubstituted alkene, we utilized high-throughput experimentation to identify a new ligand and ultimately deliver impatien A in seven steps from known compounds.
A synthetic approach to the heterodimeric bisindole alkaloid leucophyllidine is disclosed herein. An enantioenriched lactam building block, synthesized through palladium‐catalyzed asymmetric allylic ...alkylation, served as the precursor to both hemispheres. The eburnamonine‐derived fragment was synthesized through a Bischler–Napieralski/hydrogenation approach, while the eucophylline‐derived fragment was synthesized by Friedländer quinoline synthesis and two sequential C−H functionalization steps. A convergent Stille coupling and phenol‐directed hydrogenation united the two monomeric fragments to afford 16′‐epi‐leucophyllidine in 21 steps from commercial material.
A “convergent–divergent” strategy was used to synthesize the dimeric natural product leucophyllidine. An enantioenriched lactam building block was advanced in a divergent fashion to complete syntheses of both eburnamonine and eucophylline in 10 and 16 steps, respectively. A convergent cross‐coupling and hydrogenation sequence was then employed to afford 16′‐epi‐leucophyllidine (see scheme).
The asymmetric palladium‐catalyzed decarboxylative allylic alkylation of differentially N‐protected piperazin‐2‐ones allows the synthesis of a variety of highly enantioenriched tertiary ...piperazine‐2‐ones. Deprotection and reduction affords the corresponding tertiary piperazines, which can be employed for the synthesis of medicinally important analogues. The introduction of these chiral tertiary piperazines resulted in imatinib analogues which exhibited comparable antiproliferative activity to that of their corresponding imatinib counterparts.
The 'pipe'line: The title reaction allows the synthesis of highly enantioenriched tertiary piperazine‐2‐ones. Deprotection and reduction affords the corresponding tertiary piperazines, which can be employed for the synthesis of medicinally important analogues including imatinib analogues. Bz=benzoyl, PHOX=phosphinooxazoline, pmdba=bis(p‐methoxybenzylidene)acetone.
The authors of the article consider an avian disease -the respiratory mycoplasmosis of birds, its etiology, pathogenesis, description of clinical and pathoanatomical and pathohistological features of ...the course of the disease. In our country, despite the fact that there is a developed system against respiratory mycoplasmosis of birds, based on protection of farms from the introduction of infection from the outside, compliance with veterinary and sanitary rules, zoohygienic and technological standards, as well as measures aimed at timely detection of the disease, the problem of the spread of this disease is quite acute. Currently, the topic of respiratory mycoplasmosis does not lose its relevance precisely because of the high percentage of infection in poultry farms. For example, as a result of research conducted by the ARRIAH over the past 5 years, it was revealed that 218 out of 250 poultry farms in Russia were diagnosed with respiratory mycoplasmosis.
High-throughput experimentation (HTE) workflows are efficient means of surveying a broad array of chiral catalysts in the development of catalytic asymmetric reactions. However, the use of ...traditional high-pressure liquid chromatography (HPLC)-UV/vis methodology to determine enantiomeric excess (ee) from the resulting reactions is often hampered by coelution of other reaction components, resulting in erroneous ee determination when crude samples are used and ultimately requiring product isolation prior to ee analysis. In this study, using four published reactions selected as model systems, we demonstrate that the use of liquid chromatography–mass spectrometry (LC–MS), supercritical fluid chromatography–mass spectrometry (SFC-MS), and selected ion monitoring (SIM) mass chromatography provides a highly accurate means to determine the ee of products in crude reaction samples using commonplace, low-cost MS detectors. Using ion selection, coeluting signals can be deconvoluted to provide accurate integrations of the target analytes. We also show that this method is effective for samples lacking UV/vis chromophores, making it ideal for HTE workflows in asymmetric catalysis.
Objective
: to evaluate the features of reparative chondrogenesis and osteogenesis in animal experiments with the implantation of porous poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel into ...osteochondral defects.
Materials and methods
. Cylindrical pHEMA implants (5 mm in diameter) were synthesized by radical polymerization. The implants were subjected to light microscopy and mechanical tests to characterize the structure and viscoelastic properties of the material. In experimental group #1, four pHEMA specimens were implanted into formed defects in the distal femoral epiphysis of rabbits. In experimental group #2, allogeneic chondrocytes were applied to the surface of four specimens before implantation. In the control series, four defects were not replaced with implants. Tissue regeneration was investigated by morphological and morphometric methods 30 days after operation.
Results
. The pHEMA implants were heterogeneous specimens with irregularly shaped pores – up to 30 × 10 μm at the surface and 300 × 120 μm inside. With >10% static compressive stress, the Young’s modulus was 54.7 kPa. For dynamic stress, increased frequency of compression-relaxation cycles from 0.01 Hz to 20.0 Hz led to increased storage modulus from 20 kPa to 38 kPa on average, and increased loss modulus from 2 kPa to 10 kPa. Indicators of semi-quantitative assessment of local inflammatory response to pHEMA implantation had the following values in points: pHEMA, 4.7 ± 0.3; pHEMA with allogeneic chondrocytes, 6.0 ± 1.0; control, 4.3 ± 0.3. The ratio of connective, bone, and cartilage tissues proper in the regenerates had the following respective values: pHEMA, 79%, 20%, 1%; pHEMA with chondrocytes, 82%, 16%, 2%; control, 9%, 74%, 17%.
Conclusion
. In a short-term experiment, pHEMA implants did not trigger a pronounced inflammatory response in the surrounding tissues and can be classified as biocompatible materials. However, the tested implants had low conductivity with respect to bone and cartilage cells, which can be improved by stabilizing the pore size and increasing the rigidity when synthesizing the material.
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