Enantioselective construction of substituted pyridine and seven-membered carbocyclic skeleton: Biomimetic synthesis of (-)-rupestine D, (-)-guaipyridine, (-)-epiguaipyridine, (-)-cananodine and their stereoisomers

2021 ◽  
Author(s):  
Cun Zhang ◽  
Bianlin Wang ◽  
Paruke Aibibula ◽  
Jiangyu Zhao ◽  
Haji Akber Aisa
Keyword(s):  
Biomimetic Synthesis ◽  
Key Steps ◽  
Carbocyclic Skeleton

The guaipyridine alkaloids (-)-rupestine D, (-)-guaipyridine, (-)-epiguaipyridine, (-)-cananodine together with two stereoisomers 8-epi-rupestine D, and 5-epi-cananodine were synthesized enantioselectively from readily available citronellol. The key steps in this synthesis are...

Regioselective Biomimetic Synthesis of Dimeric Oxyresveratrol Derivatives

Synlett ◽  
2020 ◽  
Vol 31 (18) ◽  
pp. 1809-1812
Author(s):  
Wenling Li ◽  
Lu Ran ◽  
Hongpeng Li ◽  
Ge Chao ◽  
Xiaodong Kang ◽  
...  
Keyword(s):  
Horseradish Peroxidase ◽  
Biomimetic Synthesis ◽  
Coupling Reactions ◽  
Wittig Reactions ◽  
Key Steps ◽  
Acetone System

AbstractOxyresveratrol and its methylated derivative as coupling precursors were efficiently prepared in four steps, with Wittig reactions and subsequent isomerization reactions as the key steps. The coupling reactions of oxyresveratrol under various oxidative conditions gave a complex and inseparable mixture of coupling products. The oxidative dimerizations of methylated oxyresveratrols catalyzed by horseradish peroxidase–H2O2 or FeCl3·6H2O in an acetone system predominantly produced the 8–5-coupled and 8–10-coupled dihydrobenzofuran-type dimers, respectively. This regioselective biomimetic strategy might be useful in synthesizing other dimeric oxyresveratrol derivatives.

Biomimetic Approaches: Synthesis of (±)-Homodimericin A

Synlett ◽  
2018 ◽  
Vol 29 (07) ◽  
pp. 856-862
Author(s):  
Zhang Wang ◽  
Donghui Ma
Keyword(s):  
Total Synthesis ◽  
Usnic Acid ◽  
Biomimetic Synthesis ◽  
History Of ◽  
Key Steps

A brief history of biomimetic total synthesis is reviewed. The molecules covered in this SynPact account include tropinone (Robinson, 1917), usnic acid (Barton, 1956), progesterone (Johnson, 1971), endiandric acids (Nicolaou, 1982), methyl homosecodaphniphyllate (Heathcock, 1988), glabrescol (Corey, 2000), FR182877 (Sorensen, 2002 and Evans, 2002), and intricarene (Pattenden, 2006 and Trauner, 2006). Key biomimetic transformations of the syntheses are highlighted. Our recent biomimetic synthesis of homodimericin A is also discussed. Our study validates the key steps of the biosynthesis proposed by Clardy et al.

Reflections on the Cognitive Interviewing Reporting Framework

Methodology ◽  
2013 ◽  
Vol 9 (3) ◽  
pp. 123-128 ◽  
Author(s):  
Gordon Willis ◽  
Hennie Boeije
Keyword(s):  
Research Design ◽  
Cognitive Testing ◽  
Level Of Detail ◽  
Cognitive Interviewing ◽  
Research Groups ◽  
Research Project ◽  
Reporting Framework ◽  
Full Explanation ◽  
Key Steps

Based on the experiences of three research groups using and evaluating the Cognitive Interviewing Reporting Framework (CIRF), we draw conclusions about the utility of the CIRF as a guide to creating cognitive testing reports. Authors generally found the CIRF checklist to be usable, and that it led to a more complete description of key steps involved. However, despite the explicit direction by the CIRF to include a full explanation of major steps and features (e.g., research objectives and research design), the three cognitive testing reports tended to simply state what was done, without further justification. Authors varied in their judgments concerning whether the CIRF requires the appropriate level of detail. Overall, we believe that current cognitive interviewing practice will benefit from including, within cognitive testing reports, the 10 categories of information specified by the CIRF. Future use of the CIRF may serve to direct the overall research project from the start, and to further the goal of evaluation of specific cognitive interviewing procedures.

The development of alternative energy sources: Prospects in Russia and the world

2020 ◽  
Vol 16 (5) ◽  
pp. 885-904
Author(s):  
M.E. Frai
Keyword(s):  
Alternative Energy ◽  
Systems Approach ◽  
Energy Resource ◽  
Current Situation ◽  
Energy Sources ◽  
The Sustainable Development ◽  
Energy Complex ◽  
Alternative Energy Sources ◽  
Governmental Institutions ◽  
Key Steps

Subject. The article discusses limited sources of energy nowadays and an ongoing survey of new ones. I focus on fuel and energy complexes worldwide and in Russia. Objectives. The study is to analyze the future use of alternative energy sources in the fuel and energy complex nationwide and worldwide. I review the existing energy sources of the fuel and energy complex in the global and regional markets, specifically the alternative ones. Methods. The study relies upon methods of statistics, analysis and systems approach. Results. The article demonstrates that the fuel and energy complex strongly depends on the current situation in the energy resource market, which is difficult to forecast. If we continue relying on traditional energy resources, we get exposed to some risks affecting the sustainable development of the economy. Russia should diversify the power engineering sector by developing alternative energy sources. The article sets forth the economic rationale for alternative sources and key steps Russia shall make. Conclusions and Relevance. Considering the current situation in the energy balance, alternative energy is what any advanced society seeks for, being supported by manufacturers, governmental institutions, and researchers, though low profitability and high infrastructure costs impede its development. In Russia, these challenges are even more palpable. However, even now Russia is able to find alternative energy solutions. In addition to advantages of alternative energy, which is globally proclaimed, they will also help Russia diversify and update the economic system.

CO2 Activation on Heterostructures of Bi2O3-Nanocluster Modified TiO2: Promoting the Critical First Step in CO2 Conversion

2018 ◽  
Author(s):  
Michael Nolan
Keyword(s):  
Metal Oxide ◽  
Density Functional ◽  
Initial Step ◽  
Difficult Problem ◽  
Carbonate Formation ◽  
Structural Distortions ◽  
Strong Adsorption ◽  
Two Factors ◽  
Key Steps ◽  
Recent Experimental Work

The conversion of CO<sub>2</sub> to fuels is of significant importance in enabling the production of sustainable fuels, contributing to alleviating greenhouse gas emissions. While there are a number of key steps required to convert CO<sub>2</sub>, the initial step of adsorption and activation by the catalyst is critical. Well-known metal oxides such as oxidised TiO<sub>2</sub> or CeO<sub>2</sub> are unable to promote this step. In addressing this difficult problem, recent experimental work shows the potential for bismuth-containing materials to activate and convert CO<sub>2</sub>, but the origin of this activity is not yet clear. Additionally, nanostructures can show enhanced activity towards CO<sub>2</sub>. In this paper we present density functional theory (DFT) simulations of CO<sub>2</sub> activation on heterostructured materials composed of extended rutile and anatase TiO<sub>2</sub> surfaces modified with nanoclusters with Bi<sub>2</sub>O<sub>3</sub> stoichiometry. These heterostructures show low coordinated Bi sites in the nanoclusters and a valence band edge that is dominated by Bi-O states. These two factors mean that supported Bi<sub>2</sub>O<sub>3</sub> nanoclusters are able to adsorb and activate CO<sub>2</sub>. Computed adsorption energies lie in the range of -0.54 eV to -1.01 eV. In these strong adsorption modes, CO<sub>2</sub> is activated, in which the molecule bends giving O-C-O angles of 126 - 130<sup>o</sup> and elongation of C-O distances up to 1.28 Å, with no carbonate formation. The electronic properties show a strong CO<sub>2</sub>-Bi-oxygen interaction that drives the interaction of CO<sub>2</sub> to induce the structural distortions. Bi<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> heterostructures can be reduced to form Bi<sup>2+</sup> and Ti<sup>3+</sup> species. The interaction of CO<sub>2</sub> with this electron-rich, reduced system can produce CO directly, reoxidising the heterostructure or form an activated carboxyl species (CO<sub>2</sub><sup>-</sup>) through electron transfer from the heterostructure to CO<sub>2</sub>. These results highlight that a semiconducting metal oxide modified with suitable metal oxide nanoclusters can activate CO<sub>2</sub>, thus overcoming the difficulties associated with the difficult first step in CO<sub>2</sub> conversion.

Synthesis and Reactivity of Precolibactin 886

2019 ◽  
Author(s):  
Seth Herzon ◽  
Alan R. Healy ◽  
kevin wernke ◽  
Chung Sub Kim ◽  
Nicholas Lees ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Gene Cluster ◽  
Amino Alcohol ◽  
Biomimetic Synthesis ◽  
Cross Linking ◽  
E Coli ◽  
Hplc Purification ◽  
Structural Assignment ◽  
Biosynthetic Precursor ◽  
Double Oxidation

<div>The clb gene cluster encodes the biosynthesis of metabolites known as precolibactins and colibactins. The clb pathway is found in gut commensal E. coli, and clb metabolites are thought to initiate colorectal cancer via DNA cross-linking. Precolibactin 886 (1) is one of the most complex isolated clb metabolites; it contains a 15-atom macrocycle and an unusual 5-hydroxy-3-oxazoline ring. Here we report confirmation of the structural assignment via a biomimetic synthesis of precolibactin 886 (1) proceeding through the amino alcohol 9. Double oxidation of 9 afforded the unstable α-ketoimine 2 which underwent macrocyclization to precolibactin 886 (1) upon HPLC purification (3% from 9). Studies of the putative precolibactin 886 (1) biosynthetic precursor 2, the model α-ketoimine 25, and the α-dicarbonyl 26 revealed that these compounds are susceptible to nucleophilic rupture of the C36–C37 bond. Moreover, cleavage of 2 produces other known clb metabolites or biosynthetic intermediates. This unexpected reactivity explains the difficulties in isolating full clb metabolites and accounts for the structure of a recently identified colibactin–adenine adduct. The colibactin peptidase ClbP deacylates synthetic precolibactin 886 (1) to form a non-genotoxic pyridone, suggesting precolibactin 886 (1) lies off-path of the major biosynthetic route.</div>

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