Synthesis of Polycycles and Oxacycles by Tandem Metathesis of endo–norbornene Derivatives

Here, we have demonstrated that the presence of a carbonyl group at C7 position is preventing the olefin metathesis of endo-norbornene derivatives due to the complexation of the metal alkylidene. Time-dependent NMR studies showed the presence of new proton signals in the metal alkylidene region, which indicate the formation of metal complex with the carbonyl group of the substrate. These observations were further proved by ESI-MS analysis. Whereas, computational studies provided that the catalyst was interacting with the C7 carbonyl group and aligned perpendicular to that of norbornene olefin. Later, these endo-keto norbornene derivatives were reduced to hydroxyl derivatives diastereoselectively. Ring-rearrangement metathesis (RRM) of these hydroxyl derivatives, produced the [6/5/6], and [5/6/5] carbo-tricyclic cores of the natural products in one step. Whereas the RRM of O-allyl derivatives, delivered the oxa-tricyclic compounds in a single step with excellent yields.

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Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

10.26434/chemrxiv.10247813.v1 ◽

2019 ◽

Author(s):

Shiori Date ◽

Kensei Hamasaki ◽

Karen Sunagawa ◽

Hiroki Koyama ◽

Chikayoshi Sebe ◽

...

Keyword(s):

Natural Products ◽

Hydrogen Atom ◽

Transition Metal ◽

Hydrogen Atom Transfer ◽

Synthetic Method ◽

Atom Transfer ◽

Reaction Conditions ◽

Hydride Hydrogen ◽

Sulfur Heterocycles ◽

One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

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One-step Separation and Purification of Four Phenolic Acids from Stenoloma chusanum (L.) Ching by Medium-pressure Liquid Chromatography and High-speed Counter-current Chromatography

The Natural Products Journal ◽

10.2174/2210315508666181004115422 ◽

2019 ◽

Vol 9 (2) ◽

pp. 138-143

Author(s):

Tianyun Li ◽

Xiling Dai ◽

Yichen Li ◽

Guozheng Huang ◽

Jianguo Cao

Keyword(s):

Natural Products ◽

Liquid Chromatography ◽

Phenolic Acids ◽

High Speed ◽

High Efficiency ◽

Total Phenolic ◽

Medium Pressure ◽

Medium Pressure Liquid Chromatography ◽

One Step ◽

Counter Current

Background:Stenoloma chusanum (L.) Ching is a Chinese traditional medicinal fern with high total flavonoid and total phenolic content. Traditionally, phenolic compounds were separated by using column chromatography, which is relatively inefficient. </P><P> Objective: This study aims to use an efficient method to separate natural products from S. chusanum by Medium-Pressure Liquid Chromatography (MPLC) and High-Speed Counter-Current Chromatography (HSCCC).Methods:In the present research, firstly, a sample (2.5 g) from the dichloromethane extract of S. chusanum was separated by MPLC. Next, fraction P5 was purified by HSCCC with a two-phase solvent system composed of hexane-ethyl acetate-methanol-water (HEMWat) at a volume ratio of 2:4:1:4 (v/v/v/v). </P><P> Result: Four phenolic acids were obtained and their structures were identified by means of NMR and ESI-mass analysis. They were identified as: 1) protocatechuic acid (34 mg, purity 90.1%), 2) syringic acid (66 mg, purity 99.0%), 3) p-hydroxybenzoic acid (5 mg, purity 91.2%) and 4) vanillic acid (6 mg, purity 99.3%).Conclusion:The combination of MPLC and HSCCC is a high-efficiency separation method for natural products. This is the first report with regard to the separation of four phenolic acids in one step by MPLC and HSCCC from S. chusanum (L.) Ching.

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Single Step 2-Port Device De-Embedding Algorithm for Fixture-DUT-Fixture Network Assembly

Electronics ◽

10.3390/electronics10111275 ◽

2021 ◽

Vol 10 (11) ◽

pp. 1275

Author(s):

Simone Scafati ◽

Enza Pellegrino ◽

Francesco de Paulis ◽

Carlo Olivieri ◽

James Drewniak ◽

...

Keyword(s):

Standard Technique ◽

Single Step ◽

Scattering Parameters ◽

Linear Set ◽

S Parameter ◽

Parameter Conversion ◽

Before And After ◽

One Step ◽

Typical Measurement

The de-embedding of measurement fixtures is relevant for an accurate experimental characterization of radio frequency and digital electronic devices. The standard technique consists in removing the effects of the measurement fixtures by the calculation of the transfer scattering parameters (T-parameters) from the available measured (or simulated) global scattering parameters (S-parameters). The standard de-embedding is achieved by a multiple steps process, involving the S-to-T and subsequent T-to-S parameter conversion. In a typical measurement setup, two fixtures are usually placed before and after the device under test (DUT) allowing the connection of the device to the calibrated vector network analyzer coaxial ports. An alternative method is proposed in this paper: it is based on the newly developed multi-network cascading algorithm. The matrices involved in the fixture-DUT-fixture cascading gives rise to a non-linear set of equations that is in one step analytically solved in closed form, obtaining a unique solution. The method is shown to be effective and at least as accurate as the standard multi-step de-embedding one.

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Computational and experimental investigations of one-step conversion of poly(carbonate)s into value-added poly(aryl ether sulfone)s

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1600924113 ◽

2016 ◽

Vol 113 (28) ◽

pp. 7722-7726 ◽

Cited By ~ 29

Author(s):

Gavin O. Jones ◽

Alexander Yuen ◽

Rudy J. Wojtecki ◽

James L. Hedrick ◽

Jeannette M. García

Keyword(s):

High Performance ◽

Density Functional ◽

Value Added ◽

Single Step ◽

Nucleophilic Attack ◽

Experimental Investigations ◽

Aryl Ether ◽

One Step ◽

Poly Carbonate

It is estimated that ∼2.7 million tons poly(carbonate)s (PCs) are produced annually worldwide. In 2008, retailers pulled products from store shelves after reports of bisphenol A (BPA) leaching from baby bottles, reusable drink bottles, and other retail products. Since PCs are not typically recycled, a need for the repurposing of the PC waste has arisen. We report the one-step synthesis of poly(aryl ether sulfone)s (PSUs) from the depolymerization of PCs and in situ polycondensation with bis(aryl fluorides) in the presence of carbonate salts. PSUs are high-performance engineering thermoplastics that are commonly used for reverse osmosis and water purification membranes, medical equipment, as well as high temperature applications. PSUs generated through this cascade approach were isolated in high purity and yield with the expected thermal properties and represent a procedure for direct conversion of one class of polymer to another in a single step. Computational investigations performed with density functional theory predict that the carbonate salt plays two important catalytic roles in this reaction: it decomposes the PCs by nucleophilic attack, and in the subsequent polyether formation process, it promotes the reaction of phenolate dimers formed in situ with the aryl fluorides present. We envision repurposing poly(BPA carbonate) for the production of value-added polymers.

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Two Dimensional NMR Studies of Marine Natural Products. III.1Reassignment of the13C-NMR Spectrum of Brianthein-X Using Heteronuclear Relayed Coherence Transfer

Spectroscopy Letters ◽

10.1080/00387018608069261 ◽

1986 ◽

Vol 19 (5) ◽

pp. 545-557 ◽

Cited By ~ 4

Author(s):

Gary S. Linz ◽

M. J. Musmar ◽

Alfred J. Weinheimer ◽

Gary E. Martin ◽

James A. Matson

Keyword(s):

Natural Products ◽

Marine Natural Products ◽

Two Dimensional ◽

Coherence Transfer ◽

Nmr Studies ◽

Nmr Spectrum

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Evaluation of spermicidal activity of saponosides from Saponaria officinalis / Caryophyllaceae, Glycyrrhizia glabra / Fabaceae and Herniaria glabra / Caryophyllaceae

Medicine and Pharmacy Reports ◽

10.15386/mpr-1879 ◽

2021 ◽

Author(s):

Mohamed Réda Sefrioui ◽

Ibrahim Sbai El Othmani ◽

Halima Filali ◽

Sanae Derfoufi ◽

Soufiane Derraji ◽

...

Keyword(s):

Natural Products ◽

Side Effects ◽

Time Dependent ◽

Time Intervals ◽

Dependent Effect ◽

Time Dependent Effect ◽

Sperm Mobility ◽

In Vitro Effects ◽

Saponaria Officinalis

Background and objective. Chemical spermicides currently marketed and widely used are known to have many side effects. Thereby, and in order to look for more tolerated natural spermicidal agents, the aim of this work was to evaluate the spermicidal potential of saponin extracts from the roots of Saponaria officinalis / Caryophyllaceae, Glycyrrhizia glabra / Fabaceae, and Herniaria glabra / Caryophyllaceae by studying their in vitro effects on sperm mobility and vitality. Methods. Methanolic saponin extracts from the plants roots were performed. Sperm suspensions were prepared by centrifugation on a PureSperm® density gradient (70 and 45%) and incubated with various concentrations of saponin extracts (50, 250, 500 and 750 mg/mL) at 37°C. The spermicidal activity was evaluated by studying the mobility and vitality of spermatozoa at different time intervals ranging from 10 to 240 minutes. Results. A dose and time dependent effect on sperm mobility and vitality was observed for our extracts. Extracts from Saponaria officinalis roots induced an irreversible immobilization and a total non-viability of sperm within 10 minutes at a concentration of 750 mg/mL. A similar effect was observed within 30 minutes at 750 mg/mL for Herniaria glabra extract and within 90 minutes at 500 mg/ml for Glycyrrhizia glabra extract. Conclusion. The results of our study showed that the saponin extracts of our plants roots possess potent in vitro dose and time dependant spermicidal effect. These natural products could therefore represent a safer and better tolerated alternative to chemical spermicides.

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A Single-Step Synthesis of Azetidine-3-Amines

10.26434/chemrxiv.12846629.v1 ◽

2020 ◽

Author(s):

Brian J Wang ◽

Matthew Duncton

Keyword(s):

Functional Groups ◽

Late Stage ◽

Single Step ◽

Secondary Amines ◽

High Yield ◽

Primary Amines ◽

Privileged Structure ◽

One Step ◽

Alternative Procedures ◽

Approved Drugs

<div> <p>The azetidine group is frequently encountered within contemporary medicinal chemistry where it is viewed as a privileged structure. However, the introduction of an azetidine can be synthetically challenging. Herein, a straight-forward one step synthesis of azetidine-3-amines, starting from a bench stable, commercial material is presented. The reaction tolerates functional groups commonly encountered in biological-, medicinal- and agro-chemistry, and proceeds in moderate-to-high yield with secondary amines, and moderate-to-low yield with primary amines. The methodology compares favorably to recent alternative procedures and can be utilized in “any-stage” functionalization, including late-stage azetidinylation of approved drugs and other compounds with pharmacological activity.</p> </div>

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Three-component synthesis of highly functionalized aziridines containing a peptide side chain and their one-step transformation into β-functionalized α-ketoamides

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.12.166 ◽

2016 ◽

Vol 12 ◽

pp. 1772-1777 ◽

Cited By ~ 3

Author(s):

Lena Huck ◽

Juan F González ◽

Elena de la Cuesta ◽

J Carlos Menéndez

Keyword(s):

Single Step ◽

Side Chain ◽

One Pot ◽

Aziridine Ring ◽

Component Process ◽

Mild Conditions ◽

One Step

A sequential three-component process is described, starting from 3-arylmethylene-2,5-piperazinediones and involving a one-pot sequence of reactions achieving regioselective opening of the 2,5-diketopiperazine ring and diastereoselective generation of an aziridine ring. This method allows the preparation of N-unprotected, trisubstituted aziridines bearing a peptide side chain under mild conditions. Their transformation into β-trifluoroacetamido-α-ketoamide and α,β-diketoamide frameworks was also achieved in a single step.

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