Confined chiral Brønsted acids are shown to catalyze asymmetric oxidations of sulfides to sulfoxides with hydrogen peroxide. The wide generality and high enantioselectivity of the developed method ...compare even to the best metal-based systems and suggest utility in other asymmetric oxidations.
The accumulation of waste plastics has a severe impact on the environment, and therefore, the development of efficient chemical recycling methods has become an extremely important task. In this ...regard, a new strategy of degradation product-promoted depolymerization process was proposed. Using
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'-dimethyl-ethylenediamine (DMEDA) as a depolymerization reagent, an efficient chemical recycling of poly(bisphenol A carbonate) (BPA-PC or PC) material was achieved under mild conditions. The degradation product 1,3-dimethyl-2-imidazolidinone (DMI) was proven to be a critical factor in facilitating the depolymerization process. This strategy does not require catalysts or auxiliary solvents, making it a truly green process. This method improves the recycling efficiency of PC and promotes the development of plastic reutilization.
Abstract Background Despite the high global prevalence of prostate cancer (PCa), few epidemiologic studies have assessed physical activity in relation to PCa survival. Objective To evaluate different ...types, intensities, and timing of physical activity relative to PCa survival. Design, setting, and participants A prospective study was conducted in Alberta, Canada, in a cohort of 830 stage II–IV incident PCa cases diagnosed between 1997 and 2000 with follow-up to 2014 (up to 17 yr). Prediagnosis lifetime activity was self-reported at diagnosis. Postdiagnosis activity was self-reported up to three times during follow-up. Outcome measurements and statistical analysis Cox proportional hazards models related physical activity to all-cause and PCa-specific deaths and to first recurrence/progression of PCa. Results and limitations A total of 458 deaths, 170 PCa-specific deaths, and, after first follow-up, 239 first recurrences/progressions occurred. Postdiagnosis total activity (>119 vs ≤42 metabolic equivalent MET-hours/week per year) was associated with a significantly lower all-cause mortality risk (hazard ratio HR: 0.58; 95% confidence interval CI, 0.42–0.79; p value for trend <0.01). Postdiagnosis recreational activity (>26 vs ≤4 MET-hours/week per year) was associated with a significantly lower PCa-specific mortality risk (HR: 0.56; 95% CI, 0.35–0.90; p value for trend = 0.01). Sustained recreational activity before and after diagnosis (>18–20 vs <7–8 MET-hours/week per year) was associated with a lower risk of all-cause mortality (HR: 0.66; 95% CI, 0.49–0.88). Limitations included generalisability to healthier cases and an observational study design. Conclusions These findings support emerging recommendations to increase physical activity after the diagnosis of PCa and would inform a future exercise intervention trial examining PCa outcomes. Patient summary In a 17-yr prostate cancer (PCa) survival study, men who survived at least 2 yr who were more physically active postdiagnosis or performed more recreational physical activity before and after diagnosis survived longer. Recreational physical activity after diagnosis was associated with a lower risk of PCa death.
A range of confined iminopyridine iron complexes with skeleton of 8-(arylimino)-5,6,7-trihydroquinolyl have been prepared and well characterized by HRMS spectroscopy, FT-IR spectroscopy as well as ...elemental analysis. These iron complexes (Fe1–Fe5) serve as highly efficient pre-catalysts for conjugated dienes polymerization. By adjusting substituents of ligand framework, the stereoselectivity about 1,4-cis/trans could be switched from <1/99 to 96/4. An outstanding polymerization activity up to 108 g mol−1 h−1 was achieved with high molecular weight by employing Fe1 as pre-catalyst under optimum experimental conditions. What's more, the Fe1/MAO catalytic system showed excellent thermostability, which could lead to full conversion even at 100 °C within 10 min. Surprisingly, the polymerization activities of bio-based monomer β-farnesene and β-myrcene were able to reach 106 g mol−1 h−1 by Fe-1/MAO catalytic system, which was the highest activity of iron complex family to deliver the “green rubbers” with high molecular weights.
A range of confined iminopyridine iron complexes Fe complexes were reported in polymerization of isoprene and bio-based dienes with switchable stereoselectivity, high activity and thermostability. Display omitted
•Excellent polymerization activity up to 108 g/mol/h.•Great thermal stability with full conversion even at 100 °C.•Switchable cis/trans convertion from <1/99 to 96/4.•High molecular weight “green rubber".
Aim: Understanding the evolution of the latitudinal diversity gradient (i.e. increase in species diversity towards the tropics) is a prominent issue in ecology and biogeography. Disentangling the ...relative contributions of environment and evolutionary history in shaping this gradient remains a major challenge because their relative importance has been found to vary across regions and taxa. Here, using the global distributions and a molecular phylogeny of Rhododendron, one of the largest genera of flowering plants, we aim to compare the relative contributions of contemporary environment, evolutionary time and diversification rates in generating extant species diversity patterns. Location: Global. Time period: Undefined. Major taxa studied: Rhododendron. Methods: We compiled the global distributions of all Rhododendron species, and constructed a dated molecular phylogeny using nine chloroplast genes and seven nuclear regions. By integrating these two datasets, we estimated the temporal trends of Rhododendron diversification, and explored the global patterns of its species diversity, net diversification rates, and species ages. Next, we reconstructed the geographical ancestral area of the clade. Finally, we compared the relative contribution of contemporary environment, time-for-speciation, and diversification rates on the species diversity pattern of Rhododendron. Results: In contrast to the predictions of the time-for-speciation hypothesis, we found that although Rhododendron originated at a temperate latitude, its contemporary species diversity is highest in the tropics/subtropics, suggesting an into-the-tropics colonization for this genus. We found that the elevated diversification induced by heterogeneous environmental conditions in the tropics/subtropics shapes the global pattern of Rhododendron diversity. Main conclusions: Our findings support tropical and subtropical mountains as not only biodiversity and endemism hotspots, but also as cradles for the diversification of Rhododendron. Our study emphasizes the need of unifying ecological and evolutionary approaches in order to gain comprehensive understanding of the mechanisms underlying the global patterns of plant diversity.
Phosphorothioate nucleotides have emerged as powerful pharmacological substitutes of their native phosphodiester analogs with important translational applications in antisense oligonucleotide (ASO) ...therapeutics and cyclic dinucleotide (CDN) synthesis. Stereocontrolled installation of this chiral motif has long been hampered by the systemic use of phosphorus(III) P(III)-based reagent systems as the sole practical means of oligonucleotide assembly. A fundamentally different approach is described herein: the invention of a P(V)-based reagent platform for programmable, traceless, diastereoselective phosphorus-sulfur incorporation. The power of this reagent system is demonstrated through the robust and stereocontrolled synthesis of various nucleotidic architectures, including ASOs and CDNs, via an efficient, inexpensive, and operationally simple protocol.
Biomass waste-derived carbon materials are considered as high promising electrode materials in rechargable batteries since their wide sources, low costs and abundant reserves on earth. However, the ...structural design of these materials is still highly needed to further develop their applications in energy storage fields. In this work, peanut skin is choosen as the precursor to construct graphene-like nanosheets on the surface of porous carbon framework via a sulfuric acid-assisted hydrothermal process with following activation technique. Electrochemical results reveal this unique structure could provide high rate capacity (243 mAh·g−1 at 5 A g−1) and stable cycling performance (681 mAh·g−1 at 0.1 A g−1 after 100 cycles) in Li-ion battery and promising Na-ion storage cycling performance (233 mAh·g−1 at 0.5 A·g−1 after 450 cycles) as anodes materials. Further contrastive research indicates these promoted performance are mainly attributed to the graphene-like nanosheets in this composite structures. These sheets remarkbly enhance both of the intercalation and surface adsorption of Li-ion with high charge transfer ability, finally facilitating both of the pseudocapacitance and diffusion controlled process during the charge/discharge test. This work provides new choices for the design of nanostructures in other low cost carbonaceous materials with promoted applications in energy storage fields.
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The Catalytic Asymmetric Abramov Reaction Guin, Joyram; Wang, Qinggang; van Gemmeren, Manuel ...
Angewandte Chemie (International ed.),
January 2, 2015, Letnik:
54, Številka:
1
Journal Article
Recenzirano
The first catalytic enantioselective Abramov reaction is described. The process is based on the utilization of a chiral disulfonimide catalyst, which efficiently avoids the difficulties encountered ...with metal‐based catalysts. Several functionalized α‐hydroxy phosphonates were synthesized in good yields and with excellent enantiomeric ratios of up to >99:1. The process was shown to be scalable and up to 1 g of starting material could be employed under mild reaction conditions.
A chiral disulfonimide catalyst is used to achieve the first catalytic enantioselective Abramov reaction. Several functionalized α‐hydroxy phosphonates were synthesized in good yields and with excellent enantiomeric ratios of up to >99:1. The process was shown to be scalable and up to 1 g of starting material could be employed under mild reaction conditions.
An asymmetric Torgov cyclization, catalyzed by a novel, highly Brønsted acidic dinitro‐substituted disulfonimide, is described. The reaction delivers the Torgov diene and various analogues with ...excellent yields and enantioselectivity. This method was applied in a very short synthesis of (+)‐estrone.
A short circuit: An asymmetric Torgov cyclization, catalyzed by a novel, highly Brønsted acidic dinitro‐substituted disulfonimide, is described. The reaction delivers the Torgov diene and various analogues with excellent yields and enantioselectivity. The method was applied in a very short synthesis of (+)‐estrone.
Illustration of silanophilic interactions of phosphate prodrugs with HPLC column residual silanols in different pH mobile phases. R represents a parent compound moiety. H-bonding formation in the pH ...range of 2–5 contributes to the phosphate prodrug peak tailing discussed in this paper.
•We found silanophilic and metal–phosphate interactions are two major causes for peak tailing of phosphate prodrugs.•H bonding due to silanophilic interaction occurs at mobile phase pH from 2 to 5.•Lower acidic buffer (pH<2) should be considered if using acidic mobile phases.•Column pretreatment can reduce metal–phosphate interaction.•Non-endcapped silica columns should be avoided.
Peak tailing of phosphate prodrugs in acidic mobile phases was thoroughly investigated. The results indicated that both metal–phosphate interactions and silanophilic interactions contributed to the observed peak tailing. Column pretreatment with phosphate buffers was demonstrated to be an effective and robust approach in suppressing metal–phosphate interaction. Silanophilic interactions, such as hydrogen bonding interactions between protonated isolated silanol groups and partially deprotonated phosphate groups were mobile phase pH dependent. The combination of column pretreatment and volatile low pH mobile phase buffers can be used to mitigate peak tailing issues in developing MS compatible RPLC methods for phosphate prodrugs. The use of non-endcapped columns should be avoided in RPLC analysis for phosphate prodrugs due to large amount of residual silanol groups in the stationary phases.
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