Si-B Functional Group Exchange Reaction Enabled by a Catalytic Amount of BH3: Scope, Mechanism, and Application.

Functional group exchanges based on single-bond transformation are rare and challenging. In this regard, functional group exchange reactions of hydrosilanes proved to be more problematic. This is because this exchange requires the cleavage of the C-Si bond, while the Si-H bond is relatively easily activated for hydrosilanes. Herein, we report the first Si-B functional group exchange reactions of hydrosilanes with hydroboranes simply enabled by BH3 as a catalyst. Our methodology works for various aryl and alkyl hydrosilanes and different hydroboranes with the tolerance of general functional groups (up to 115 examples). Control experiments and density functional theory (DFT) studies reveal a distinct reaction pathway that involves consecutive C-Si/B-H and C-B/B-H σ-bond metathesis. Further investigations of using more readily available chlorosilanes, siloxane, fluorosilane, and silylborane for Si-B functional group exchanges, Ge-B functional group exchanges, and depolymerizative Si-B exchanges of polysilanes are also demonstrated. Moreover, the regeneration of MeSiH3 from polymethylhydrosiloxane (PMHS) is achieved. Notably, the formal hydrosilylation of a wide range of alkenes with SiH4 and MeSiH3 to selectively produce (chiral)trihydrosilanes and (methyl)dihydrosilanes is realized using inexpensive and readily available PhSiH3 and PhSiH2Me as gaseous SiH4 and MeSiH3 surrogates.

Linking phytosterols and oxyphytosterols from food to brain health: origins, effects, and underlying mechanisms.

Phytosterols and their oxidation products, namely oxyphytosterols, are natural compounds present in plant foods. With increased intake of phytosterol-enriched functional food products, the exposure of both phytosterols and oxyphytosterols is rising. Over the past ten years, researches have been focused on their absorption and metabolism in human body, as well as their biological effects. More importantly, recent studies showed that phytosterols and oxyphytosterols can traverse the blood-brain barrier and accumulate in the brain. As brain health problems resulting from ageing being more serious, attenuating central nervous system (CNS) disorders with active compounds in food are becoming a hot topic. Phytosterols and oxyphytosterols have been shown to implicated in cognition altering and the pathologies of several CNS disorders, including Alzheimer's disease and multiple sclerosis. We will overview these findings with a focus on the contents of phytosterols and oxyphytosterols in food and their dietary intake, as well as their origins in the brain, and illustrate molecular pathways through which they affect brain health, in terms of inflammation, cholesterol homeostasis, oxidative stress, and mitochondria function. The existing scientific gaps of phytosterols and oxyphytosterols to brain health in knowledge are also discussed, highlighting research directions in the future.

H2B ubiquitylation promotes RNA Pol II processivity via PAF1 and pTEFb.

Histone H2B ubiquitination plays an important role in transcription regulation. It has been shown that H2B ubiquitination is regulated by multiple upstream events associated with elongating RNA polymerase. Here we demonstrate that H2B K34 ubiquitylation by the MOF-MSL complex is part of the protein networks involved in early steps of transcription elongation. Knocking down MSL2 in the MOF-MSL complex affects not only global H2BK34ub, but also multiple cotranscriptionally regulated histone modifications. More importantly, we show that the MSL, PAF1, and RNF20/40 complexes are recruited and stabilized at active gene promoters by direct binary interactions. The stabilized complexes serve to regulate chromatin association of pTEFb through a positive feedback loop and facilitate Pol II transition during early transcription elongation. Results from our biochemical studies are underscored by genome-wide analyses that show high RNA Pol II processivity and transcription activity at MSL target genes.

Titanium-Catalyzed Exhaustive Reduction of Oxo-Chemicals.

Catalytic reduction of carboxylic acids and derivatives all the way to their corresponding methyl-compounds is very rare and still challenging for homogeneous transition-metal catalysis. Herein, we report an unprecedented and general catalytic exhaustive reduction of carboxylic functional group straightforwardly to a methyl group. This reaction was achieved using earth-abundant and readily available titanium as a catalyst. Our system has broad functional group tolerance and works for various other types of oxo-chemicals such as alcohols, aldehydes, ketones, lactones, and carboxylates (>100 examples). Preliminary mechanistic studies revealed that the in situ-generated TiIII -H species was vital for this transformation.

ASH2L regulates ubiquitylation signaling to MLL: trans-regulation of H3 K4 methylation in higher eukaryotes.

Crosstalk between H2B ubiquitylation (H2Bub) and H3 K4 methylation plays important roles in coordinating functions of diverse cofactors during transcription activation. The underlying mechanism for this trans-tail signaling pathway is poorly defined in higher eukaryotes. Here, we show the following: (1) ASH2L in the MLL complex is essential for H2Bub-dependent H3 K4 methylation. Deleting or mutating K99 of the N-terminal winged helix (WH) motif in ASH2L abrogates H2Bub-dependent regulation. (2) Crosstalk can occur in trans and does not require ubiquitin to be on nucleosomes or histones to exert regulatory effects. (3) trans-regulation by ubiquitin promotes MLL activity for all three methylation states. (4) MLL3, an MLL homolog, does not respond to H2Bub, highlighting regulatory specificity for MLL family histone methyltransferases. Altogether, our results potentially expand the classic histone crosstalk to nonhistone proteins, which broadens the scope of chromatin regulation by ubiquitylation signaling.

Effects of soil amendments on fractions and stability of soil organic matter in saline-alkaline paddy.

Soil amelioration is an effective practice to alleviate the adverse effects of soil salinization. However, increasing the fertility of salt-affected soils has been challenging, particularly in coastal saline-alkaline paddy soils. Here, we carried out a 45-day incubation experiment to evaluate the impacts of soil amendments on fractions and stability of soil organic matter (SOM) in a saline-alkaline paddy. The experiment simulates the flooding-draining practice and consists of CaCO3, gypsum and biochar amendments using different fertility soils. We measured dissolved organic carbon (DOC) and nitrogen (DON) in supernatant liquids, water-soluble cations, water extractable organic carbon (WEOC) and nitrogen (WEON), and microbial biomass carbon (MBC) and nitrogen (MBN) in soils after the incubation. Results showed that water soluble sodium (Na+) was significantly decreased under all amendments (by 17%-32%), except in high fertility soil. We found a significant decrease in DOC (by 36%-47%) under gypsum treatment, but in DON (by 18%-59%) under biochar treatment. However, there was no significant effect on DOC or DON under CaCO3 treatment. Gypsum treatment led to decreased WEOC content (by 0.067%-5.4%), but increased MBC (by 0.16%-44%) and MBN (by 8.3%-37%) in all soils. Biochar treatment caused a decrease in the ratios of WEOC to soil organic carbon (SOC) and WEON to total nitrogen (TN), and an increase in MBC:SOC and MBN:TN ratios. These results suggest that gypsum and biochar amendments can enhance SOM stability in the saline-alkaline paddy. However, SOM stability was not enhanced under CaCO3 treatment, probably due to the presence of a large amount of Na+ in these soils. Our study highlights that soil amelioration has different effects on soil carbon and nitrogen cycles in the saline-alkaline paddy soils, which is associated with water-logged condition.

Catalytic Boration of Alkyl Halides with Borane without Hydrodehalogenation Enabled by Titanium Catalyst.

An unprecedented and general titanium-catalyzed boration of alkyl (pseudo)halides (alkyl-X, X=I, Br, Cl, OMs) with borane (HBpin, HBcat) is reported. The use of titanium catalyst can successfully suppress the undesired hydrodehalogenation products that prevail using other transition-metal catalysts. A series of synthetically useful alkyl boronate esters are readily obtained from various (primary, secondary, and tertiary) alkyl electrophiles, including unactivated alkyl chlorides, with tolerance of other reducing functional groups such as ester, alkene, and carbamate. Preliminary studies on the mechanism revealed a possible radical reaction pathway. Further extension of our strategy to aryl bromides is also demonstrated.

Site-Fixed Hydroboration of Terminal and Internal Alkenes using BX3 /i Pr2 NEt*.

An unprecedented and general hydroboration of alkenes with BX3 (X=Br, Cl) as the boration reagent in the presence of i Pr2 NEt is reported. The addition of i Pr2 NEt not only suppresses alkene polymerization and haloboration side reactions but also provides an "H" source for hydroboration. More importantly, the site-fixed installation of a boryl group at the original position of the internal double bond is readily achieved in contrast to conventional transition-metal-catalyzed hydroboration processes. Further application to the synthesis of 1,n-diborylalkanes (n=3-10) is also demonstrated. Preliminary mechanistic studies reveal a major reaction pathway that involves radical species and operates through a frustrated Lewis pair type single-electron-transfer mechanism.

Therapeutic potential of phenylethanoid glycosides: A systematic review.

Phenylethanoid glycosides (PhGs) are generally water-soluble phenolic compounds that occur in many medicinal plants. Until June 2020, more than 572 PhGs have been isolated and identified. PhGs possess antibacterial, anticancer, antidiabetic, anti-inflammatory, antiobesity, antioxidant, antiviral, and neuroprotective properties. Despite these promising benefits, PhGs have failed to fulfill their therapeutic applications due to their poor bioavailability. The attempts to understand their metabolic pathways to improve their bioavailability are investigated. In this review article, we will first summarize the number of PhGs compounds which is not accurate in the literature. The latest information on the biological activities, structure-activity relationships, mechanisms, and especially the clinical applications of PhGs will be reviewed. The bioavailability of PhGs will be summarized and factors leading to the low bioavailability will be analyzed. Recent advances in methods such as bioenhancers and nanotechnology to improve the bioavailability of PhGs are also summarized. The existing scientific gaps of PhGs in knowledge are also discussed, highlighting research directions in the future.

Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes.

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Zirconium-Catalyzed Atom-Economical Synthesis of 1,1-Diborylalkanes from Terminal and Internal Alkenes.

A general and atom-economical synthesis of 1,1-diborylalkanes from alkenes and a borane without the need for an additional H2 acceptor is reported for the first time. The key to our success is the use of an earth-abundant zirconium-based catalyst, which allows a balance of self-contradictory reactivities (dehydrogenative boration and hydroboration) to be achieved. Our method avoids using an excess amount of another alkene as an H2 acceptor, which was required in other reported systems. Furthermore, substrates such as simple long-chain aliphatic alkenes that did not react before also underwent 1,1-diboration in our system. Significantly, the unprecedented 1,1-diboration of internal alkenes enabled the preparation of 1,1-diborylalkanes.

The RING finger protein MSL2 in the MOF complex is an E3 ubiquitin ligase for H2B K34 and is involved in crosstalk with H3 K4 and K79 methylation.

We demonstrate that RING finger protein MSL2 in the MOF-MSL complex is a histone ubiquitin E3 ligase. MSL2, together with MSL1, has robust histone ubiquitylation activity that mainly targets nucleosomal H2B on lysine 34 (H2B K34ub), a site within a conserved basic patch on H2B tail. H2B K34ub by MSL1/2 directly regulates H3 K4 and K79 methylation through trans-tail crosstalk both in vitro and in cells. The significance of MSL1/2-mediated histone H2B ubiquitylation is underscored by the facts that MSL1/2 activity is important for transcription activation at HOXA9 and MEIS1 loci and that this activity is evolutionarily conserved in the Drosophila dosage compensation complex. Altogether, these results indicate that the MOF-MSL complex possesses two distinct chromatin-modifying activities (i.e., H4 K16 acetylation and H2B K34 ubiquitylation) through MOF and MSL2 subunits. They also shed light on how an intricate network of chromatin-modifying enzymes functions coordinately in gene activation.

FOXP3 orchestrates H4K16 acetylation and H3K4 trimethylation for activation of multiple genes by recruiting MOF and causing displacement of PLU-1.

Both H4K16 acetylation and H3K4 trimethylation are required for gene activation. However, it is still largely unclear how these modifications are orchestrated by transcriptional factors. Here, we analyzed the mechanism of the transcriptional activation by FOXP3, an X-linked suppressor of autoimmune diseases and cancers. FOXP3 binds near transcriptional start sites of its target genes. By recruiting MOF and displacing histone H3K4 demethylase PLU-1, FOXP3 increases both H4K16 acetylation and H3K4 trimethylation at the FOXP3-associated chromatins of multiple FOXP3-activated genes. RNAi-mediated silencing of MOF reduced both gene activation and tumor suppression by FOXP3, while both somatic mutations in clinical cancer samples and targeted mutation of FOXP3 in mouse prostate epithelial cells disrupted nuclear localization of MOF. Our data demonstrate a pull-push model in which a single transcription factor orchestrates two epigenetic alterations necessary for gene activation and provide a mechanism for somatic inactivation of the FOXP3 protein function in cancer cells.

H2 -Acceptorless Dehydrogenative Boration and Transfer Boration of Alkenes Enabled by Zirconium Catalyst.

The first example of an efficient and direct dehydrogenative boration of alkenes for vinyl boronate ester synthesis was achieved using a zirconium catalyst. Our methodology avoids using precious transition metals, additional hydrogen acceptors, high temperatures, and long reaction times, which were required to overcome the reducing ability of borane, to give alkyl boronate esters. Detailed mechanistic studies revealed a reversible reaction pathway and further suggested applying the zirconium complex as a "shuttle catalyst" for transfer boration, which thus sidesteps the use of relatively sensitive borane.

Non-Metal-Catalyzed Heterodehydrocoupling of Phosphines and Hydrosilanes: Mechanistic Studies of B(C6F5)3-Mediated Formation of P-Si Bonds.

Non-metal-catalyzed heterodehydrocoupling of primary and secondary phosphines (R1R2PH, R2 = H or R1) with hydrosilanes (R3R4R5SiH, R4, R5 = H or R3) to produce synthetically useful silylphosphines (R1R2P-SiR3R4R5) has been achieved using B(C6F5)3 as the catalyst (10 mol %, 100 °C). Kinetic studies demonstrated that the reaction is first-order in hydrosilane and B(C6F5)3 but zero-order in phosphine. Control experiments, DFT calculations, and DOSY NMR studies suggest that a R1R2HP·B(C6F5)3 adduct is initially formed and undergoes partial dissociation to form an "encounter complex". The latter mediates frustrated Lewis pair type Si-H bond activation of the silane substrates. We also found that B(C6F5)3 catalyzes the homodehydrocoupling of primary phosphines to form cyclic phosphine rings and the first example of a non-metal-catalyzed hydrosilylation of P-P bonds to produce silylphosphines (R1R2P-SiR3R4R5). Moreover, the introduction of PhCN to the reactions involving secondary phosphines with hydrosilanes allowed the heterodehydrocoupling reaction to proceed efficiently under much milder conditions (1.0 mol % B(C6F5)3 at 25 °C). Mechanistic studies, as well as DFT calculations, revealed that PhCN plays a key mechanistic role in facilitating the dehydrocoupling reactions rather than simply functioning as H2-acceptor.

Two mammalian MOF complexes regulate transcription activation by distinct mechanisms.

In mammals, MYST family histone acetyltransferase MOF plays important roles in transcription activation by acetylating histone H4 on K16, a prevalent mark associated with chromatin decondensation, and transcription factor p53 on K120, which is important for activation of proapoptotic genes. However, little is known about MOF regulation in higher eukaryotes. Here, we report that the acetyltransferase activity of MOF is tightly regulated in two different but evolutionarily conserved complexes, MSL and MOF-MSL1v1. Importantly, we demonstrate that while the two MOF complexes have indistinguishable activity on histone H4 K16, they differ dramatically in acetylating nonhistone substrate p53. We further demonstrate that MOF-MSL1v1 is specifically required for optimal transcription activation of p53 target genes both in vitro and in vivo. Our results support a model that these two MOF complexes regulate distinct stages of transcription activation in cooperation with other histone modifying activities.

Acaricidal Activity and Synergistic Effect of Thyme Oil Constituents against Carmine Spider Mite (Tetranychus Cinnabarinus (Boisduval)).

Studies examining the use of essential oils as replacements for synthetic insecticides require an understanding of the contribution of each constituent present, interactions among these components, and how they relate to overall toxicity. In the present study, the chemical composition of commercial thyme oil was identified by gas chromatography-mass spectrometry. Thyme oil and blends of its major constituents were tested for their acaricidal activitities against carmine spider mites (Tetranychus cinnabarinus (Boisduval)) using a slide-dip bioassay. Natural thyme oil showed greater toxicity than any single constituent or blend of constituents. Thymol was the most abundant component (34.4%), and also possessed the strongest acaricidal activity compared with other single constituents. When tested individually, four constituents (linalool, terpinene, p-cymene and carvacrol) also had activity, while α-pinene, benzoic acid and ethyl gallate had almost no activity. The toxicity of blends of selected constituents indicated a synergistic effect among the putatively active and inactive constituents, with the presence of all constituents necessary to reach the highest toxicity. The results indicated that thyme oil and some of its major constituents have the potential to be developed into botanical acaricides.

Transition-metal-catalyzed carbonylation reactions of olefins and alkynes: a personal account.

Carbon monoxide was discovered and identified in the 18th century. Since the first applications in industry 80 years ago, academic and industrial laboratories have broadly explored CO's use in chemical reactions. Today organic chemists routinely employ CO in organic chemistry to synthesize all kinds of carbonyl compounds. Despite all these achievements and a century of carbonylation catalysis, many important research questions and challenges remain. Notably, apart from academic developments, industry applies carbonylation reactions with CO on bulk scale. In fact, today the largest applications of homogeneous catalysis (regarding scale) are carbonylation reactions, especially hydroformylations. In addition, the vast majority of acetic acid is produced via carbonylation of methanol (Monsanto or Cativa process). The carbonylation of olefins/alkynes with nucleophiles, such as alcohols and amines, represent another important type of such reactions. In this Account, we discuss our work on various carbonylations of unsaturated compounds and related reactions. Rhodium-catalyzed isomerization and hydroformylation reactions of internal olefins provide straightforward access to higher value aldehydes. Catalytic hydroaminomethylations offer an ideal way to synthesize substituted amines and even heterocycles directly. More recently, our group has also developed so-called alternative metal catalysts based on iridium, ruthenium, and iron. What about the future of carbonylation reactions? CO is already one of the most versatile C1 building blocks for organic synthesis and is widely used in industry. However, because of CO's high toxicity and gaseous nature, organic chemists are often reluctant to apply carbonylations more frequently. In addition, new regulations have recently made the transportation of carbon monoxide more difficult. Hence, researchers will need to develop and more frequently use practical and benign CO-generating reagents. Apart from formates, alcohols, and metal carbonyls, carbon dioxide also offers interesting options. Industrial chemists seek easy to prepare catalysts and patent-free ligands/complexes. In addition, non-noble metal complexes will interest both academic and industrial researchers. The novel Lucite process for methyl methacrylate is an important example of an improved catalyst. This reaction makes use of a specific palladium/bisphosphine catalyst, which led to the successful implementation of the technology. More active and productive catalysts for related carbonylations of less reactive olefins would allow for other large scale applications of this methodology. From an academic point of view, researchers continue to look for selective reactions with more functionalized olefins. Finally, because of the volatility of simple metal carbonyl complexes, carbonylation reactions today remain a domain of homogeneous catalysis. The invention of more stable and recyclable heterogeneous catalysts or metal-free carbonylations (radical carbonylations) will be difficult, but could offer interesting challenges for young chemists.

Applicability of the Tanaka-Johnston and Moyers mixed dentition analyses in Northeast Han Chinese.

OBJECTIVES: To assess applicability of the Tanaka-Johnston and Moyers prediction methods in a Han ethnic group from Northeast China and to develop prediction equations for this same population. DESIGN: Cross-sectional study. SETTING: Department of Orthodontics, School of Stomatology, Jiamusi University, Heilongjiang, China. PARTICIPANTS: A total of 130 subjects (65 male and 65 female) aged 16-21 years from a Han ethnic group of Northeast China were recruited from dental students and patients seeking orthodontic treatment. Ethnicity was verified by questionnaire. MATERIAL AND METHODS: Mesio-distal tooth width was measured using Digital Vernier calipers. Predicted values were obtained from the Tanaka-Johnston and Moyers methods in both arches were compared with the actual measured widths. Based on regression analysis, prediction equations were developed. RESULTS: Tanaka-Johnston equations were not precise, except for the upper arch in males. However, the Moyers 85th percentile in the upper arch and 75th percentile in the lower arch predicted the sum precisely in males. For females, the Moyers 75th percentile predicted the sum precisely for the upper arch, but none of the Moyers percentiles predicted in the lower arch. CONCLUSIONS: Both the Tanaka-Johnston and Moyers method may not be applied universally without question. Hence, it may be safer to develop regression equations for specific populations. Validating studies must be conducted to confirm the precision of these newly developed regression equations.

Development of a ruthenium/phosphite catalyst system for domino hydroformylation-reduction of olefins with carbon dioxide.

An efficient domino ruthenium-catalyzed reverse water-gas-shift (RWGS)-hydroformylation-reduction reaction of olefins to alcohols is reported. Key to success is the use of specific bulky phosphite ligands and triruthenium dodecacarbonyl as the catalyst. Compared to the known ruthenium/chloride system, the new catalyst allows for a more efficient hydrohydroxymethylation of terminal and internal olefins with carbon dioxide at lower temperature. Unwanted hydrogenation of the substrate is prevented. Preliminary mechanism investigations uncovered the homogeneous nature of the active catalyst and the influence of the ligand and additive in individual steps of the reaction sequence.