scholarly journals Synthetic Studies Towards Spirocyclic Imine Marine Toxins Using N-Acyl Iminium Ions as Dienophiles in Diels–Alder Reactions

Synlett ◽  
2020 ◽  
Vol 31 (07) ◽  
pp. 657-671
Author(s):  
Jared L. Freeman ◽  
Freda F. Li ◽  
Daniel P. Furkert ◽  
Margaret A. Brimble
Keyword(s):  
Biological Activities ◽  
Diels Alder ◽  
Direct Access ◽  
Marine Toxins ◽  
Chemical Structures ◽  
Marine Toxin ◽  
Iminium Ions ◽  
Iminium Ion ◽  
Novel Method

Cyclic imine marine toxins have attracted considerable attention from the synthetic community in the past two decades due to their unique chemical structures and clinically relevant biological activities. This review presents recent efforts of our group in the development of various strategies to efficiently construct the common spirocyclic imine fragments of the cyclic imine toxins. In particular, the use of α,β-unsaturated N-acyl iminium ion dienophiles in Diels–Alder reactions are highlighted, whereby direct access to spirocyclic imine motifs was obtained and important mechanistic details were discovered. Alternative approaches to spirocyclic imine systems involving hydroamination of amino alkynes are also summarized. One such approach led to serendipitous access to N-vinyl amide products, while our most recently ­reported approach involving an intermolecular Diels–Alder/cross-­coupling sequence using novel 2-bromo-1,3-butadienes to access 5,6-spirocyclic imines is also discussed. Additionally, the development of a novel method to construct another challenging motif present in the portimines is also introduced.1 Introduction2 Strategies towards the Spirocyclic Imine Fragment of Cyclic Imine Toxins2.1 Diels–Alder Cycloadditions of α,β-Unsaturated N-Acyl Iminium Dienophiles2.2 Early Studies Using in situ-Generated Iminium Ion Dienophiles2.3 Use of More Stable Iminium Ion Dienophiles for Diels–Alder Reactions2.4 Other Notable Strategies towards Spirocyclic Imines2.5 Recent Efforts towards the 5,6-Spirocyclic Imine Marine Toxin Portimine A2.6 Construction of Another Challenging Motif of Portimine A3 Conclusion and Future Perspectives

scholarly journals Direct Synthesis of Phosphonates and α-Amino-phosphonates from 1,3-Benzoxazines

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 294 ◽  
Author(s):  
Oscar Salgado-Escobar ◽  
Alexis Hernández-Guadarrama ◽  
Ivan Romero-Estudillo ◽  
Irma Linzaga-Elizalde
Keyword(s):  
Michael Addition ◽  
Addition Reaction ◽  
Direct Synthesis ◽  
Boron Trifluoride Etherate ◽  
Quinone Methide ◽  
Michael Addition Reaction ◽  
Iminium Ion ◽  
Novel Method ◽  
Amino Phosphonates

A straightforward and novel method for transformation of readily available 1,3-benzoxazines to secondary phosphonates and α-aminophosphonates using boron trifluoride etherate as catalyst is developed. The formation of phosphonates proceeds through ortho-quinone methide (o-QM) generated in situ, followed by a phospha-Michael addition reaction. On the other hand, the α-aminophosphonates were obtained by iminium ion formation and the subsequence nucleophilic substitution of alkylphosphites. This method can be also used for the preparation of o-hydroxybenzyl ethers through oxa-Michael addition.

Technique for repetitive recording from fetal respiratory neurons

1996 ◽  
Vol 80 (3) ◽  
pp. 1057-1060
Author(s):  
S. Ioffe ◽  
A. H. Jansen ◽  
V. Chernick
Keyword(s):  
Time Span ◽  
Direct Access ◽  
Respiratory Neurons ◽  
Intracellular Recordings ◽  
Recording Electrode ◽  
Fetal Head ◽  
Fetal Sheep ◽  
Novel Method ◽  
Medullary Neurons

We developed a new method for repetitive recording of medullary neurons in fetal sheep in situ. The technique involves chronically fixing the fetal head to the flank of the ewe by way of a Teflon plate that has a removable window. This window allows direct access of a recording electrode to the floor of the fourth ventricle of the fetus. In four of six fetuses, repetitive recordings lasting 3-4 h were possible for up to 6 days. By operating on younger fetuses and with care, this time span could be extended. This novel method should be useful in the future for extracellular and intracellular recordings of neurons in the developing fetus without disturbing the fetal state and for the study of putative neurotransmitters during development with iontophoretic techniques.

Design, Synthesis, Characterization and in silico molecular docking studies and in vivo anti-inflammatory Activity of Pyrazoline clubbed Thiazolinone Derivatives

2020 ◽  
Vol 17 ◽  
Author(s):  
Deepak Kumar Singh ◽  
Mayank Kulshreshtha ◽  
Yogesh Kumar ◽  
Pooja A Chawla ◽  
Akash Ved ◽  
...  
Keyword(s):  
Molecular Docking ◽  
Biological Activities ◽  
Inflammatory Activity ◽  
Standard Drug ◽  
Docking Score ◽  
Chemical Structures ◽  
Cox 2 ◽  
Anti Inflammatory ◽  
Cox 1

Background: The pyrazolines give the reactions of aliphatic derivatives, resembling unsaturated compounds in their behavior towards permanganate and nascent hydrogen. This nucleus has been associated with various biological activities including inflammatory. Thiazolinone is a heterocyclic compound that contains both sulfur and nitrogen atom with a carbonyl group in their structure.Thiazolinone and their derivatives have attracted continuing interest because of their various biological activities, such as anti-inflammatory, antimicrobial, anti-proliferative, antiviral, anticonvulsant etc. The aim of the research was to club pyrazoline nucleus with thiazolinone in order to have significantanti-inflammatory activity. The synthesized compounds were chemically characterized for the establishment of their chemical structures and to evaluate as anti-inflammatory agent. Method: In the present work, eight derivatives of substituted pyrazoline (PT1-PT8) were synthesized by a three step reaction.The compounds were subjected to spectral analysis by Infrared, Mass and Nuclear magnetic resonance spectroscopy and elemental analysis data. All the synthesized were evaluated for their in vivo anti-inflammatory activity. The synthesized derivatives were evaluated for their affinity towards target COX-1 and COX-2, using indomethacin as the reference compound molecular docking visualization through AutoDock Vina. Results: Compounds PT-1, PT-3, PT-4 and PT-8 exhibited significant anti-inflammatory activity at 3rd hour being 50.7%, 54.3%, 52.3% and 57% respectively closer to that of the standard drug indomethacin (61.9%).From selected anti-inflammatory targets, the synthesized derivatives exhibited better interaction with COX-1 and COX-2 receptor, where indomethacin showed docking score of -6.5 kJ/mol, compound PT-1 exhibited highest docking score of -9.1 kJ/mol for COX-1 and compound PT-8 having docking score of 9.4 kJ/mol for COX-2. Conclusion: It was concluded that synthesized derivatives have more interaction with COX-2 receptors in comparison to the COX-1 receptors because the docking score with COX-2 receptors were very good. It is concluded that the synthesized derivatives (PT-1 to PT-8) are potent COX-2 inhibitors.

Biotransformation of Coumarins by Filamentous Fungi: An Alternative Way for Achievement of Bioactive Analogs

2019 ◽  
Vol 16 (6) ◽  
pp. 568-577 ◽  
Author(s):  
Jainara Santos do Nascimento ◽  
João Carlos Silva Conceição ◽  
Eliane de Oliveira Silva
Keyword(s):  
Filamentous Fungi ◽  
Chemical Reactions ◽  
Biological Activities ◽  
Chemical Transformations ◽  
Chemical Structures ◽  
Pattern Structures ◽  
Pharmacological Interest ◽  
Aspergillus Sp ◽  
The Impact ◽  
Related Compounds

Coumarins are natural 1,2-benzopyrones, present in remarkable amounts as secondary metabolites in edible and medicinal plants. The low yield in the coumarins isolation from natural sources, along with the difficulties faced by the total synthesis, make them attractive for biotechnological studies. The current literature contains several reports on the biotransformation of coumarins by fungi, which can generate chemical analogs with high selectivity, using mild and eco-friendly conditions. Prompted by the enormous pharmacological interest in the coumarin-related compounds, their alimentary and chemical applications, this review covers the biotransformation of coumarins by filamentous fungi. The chemical structures of the analogs were presented and compared with those from the pattern structures. The main chemical reactions catalyzed the insertion of functional groups, and the impact on the biological activities caused by the chemical transformations were discussed. Several chemical reactions can be catalyzed by filamentous fungi in the coumarin scores, mainly lactone ring opening, C3-C4 reduction and hydroxylation. Chunninghamella sp. and Aspergillus sp. are the most common fungi used in these transformations. Concerning the substrates, the biotransformation of pyranocoumarins is a rarer process. Sometimes, the bioactivities were improved by the chemical modifications and coincidences with the mammalian metabolism were pointed out.

Anticancer Active Heterocyclic Chalcones: Recent Developments

2020 ◽  
Vol 20 ◽  
Author(s):  
Prasad Dandawate ◽  
Khursheed Ahmed ◽  
Subhash Padhye ◽  
Aamir Ahmad ◽  
Bernhard Biersack
Keyword(s):  
Histone Deacetylases ◽  
Biological Activities ◽  
Synthetic Methods ◽  
Antitumor Activities ◽  
Web Based ◽  
Chemical Structures ◽  
Recent Developments ◽  
Number Of Publications ◽  
Tubulin Polymerization Inhibitors ◽  
Dna Binding Properties

Background: Chalcones are structurally simple compounds that are easily accessible by synthetic methods. Heterocyclic chalcones have gained the interest among scientists due to their diverse biological activities. The anti-tumor activities of heterocyclic chalcones are especially remarkable and the growing number of publications dealing with this topic warrants an up-to-date compilation. Methods: Search for antitumor active heterocyclic chalcones was carried out using Pubmed and Scifinder as common web-based literature searching tools. Pertinent and current literature is covered from 2015/2016 to 2019. Chemical structures, biological activities and modes of action of anti-tumor active heterocyclic chalcones are summarized. Results: Simply prepared chalcones have emerged over the last years with promising antitumor activities. Among them is a considerable number of tubulin polymerization inhibitors. But there are also new chalcones targeting special enzymes such as histone deacetylases or with DNA-binding properties. Conclusion: This review provides a summary of recent heterocyclic chalcone derivatives with distinct anti-tumor activities.

scholarly journals Sphingolipids of Asteroidea and Holothuroidea: Structures and Biological Activities

Marine Drugs ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. 330
Author(s):  
Timofey V. Malyarenko ◽  
Alla A. Kicha ◽  
Valentin A. Stonik ◽  
Natalia V. Ivanchina
Keyword(s):  
Marine Invertebrates ◽  
Biological Activities ◽  
Complete Information ◽  
Structural Features ◽  
Marine Organisms ◽  
Structural Components ◽  
Chemical Structures ◽  
The Past ◽  
Complex Lipids ◽  
Complex Sphingolipids

Sphingolipids are complex lipids widespread in nature as structural components of biomembranes. Commonly, the sphingolipids of marine organisms differ from those of terrestrial animals and plants. The gangliosides are the most complex sphingolipids characteristic of vertebrates that have been found in only the Echinodermata (echinoderms) phylum of invertebrates. Sphingolipids of the representatives of the Asteroidea and Holothuroidea classes are the most studied among all echinoderms. In this review, we have summarized the data on sphingolipids of these two classes of marine invertebrates over the past two decades. Recently established structures, properties, and peculiarities of biogenesis of ceramides, cerebrosides, and gangliosides from starfishes and holothurians are discussed. The purpose of this review is to provide the most complete information on the chemical structures, structural features, and biological activities of sphingolipids of the Asteroidea and Holothuroidea classes.

scholarly journals Influencing Factors on the Physicochemical Characteristics of Tea Polysaccharides

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3457
Author(s):  
Ting Hu ◽  
Peng Wu ◽  
Jianfeng Zhan ◽  
Weixin Wang ◽  
Junfeng Shen ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Biological Activities ◽  
Structural Difference ◽  
Physicochemical Characteristics ◽  
Bioactive Constituents ◽  
Preparation Methods ◽  
Processing Technologies ◽  
Chemical Structures ◽  
Tea Polysaccharides ◽  
Fine Structures

Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.

scholarly journals Development of a novel method for the in-situ dechlorination of immovable iron elements: optimization of Cl− extraction yield through experimental design

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marco Veneranda ◽  
Nagore Prieto-Taboada ◽  
Jose Antonio Carrero ◽  
Ilaria Costantini ◽  
Aitor Larrañaga ◽  
...  
Keyword(s):  
Experimental Design ◽  
Optimization Design ◽  
Degradation Process ◽  
Extraction Yield ◽  
Alkaline Solutions ◽  
Iron Core ◽  
Total Consumption ◽  
Iron Leaching ◽  
Novel Method

AbstractThe conservation of iron objects exposed to marine aerosol is threatened by the formation of akaganeite, a highly unstable Cl-bearing corrosion phase. As akaganeite formation is responsible of the exfoliation of the rust layer, chlorides trigger a cyclic alteration phenomenon that often ends with the total consumption of the iron core. To prevent this degradation process, movable iron elements (e.g. archaeometallurgical artefacts) are generally immersed in alkaline dechlorination baths. Aiming to transfer this successful method to the treatment of immovable iron objects, we propose the in-situ application of alkaline solutions through the use of highly absorbent wraps. As first step of this novel research line, the present work defines the best desalination solution to be used and optimizes its extraction yield. After literature review, a screening experimental design was performed to understand the single and synergic effects of common additives used for NaOH baths. Once the most effective variables were selected, an optimization design was carried out to determine the optimal conditions to be set during treatment. According to the experimental work here presented, the use of 0.7 M NaOH solutions applied at high temperatures (above 50 °C) is recommended. Indeed, these conditions enhance chloride extraction and iron leaching inhibition, while promoting corrosion stabilization.

scholarly journals A Further Comprehensive Review on the Phytoconstituents from the Genus Erythrina

2020 ◽  
Vol 23 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Mohammad Musarraf Hussain
Keyword(s):  
Chemical Structure ◽  
Biological Activities ◽  
Chemical Constituents ◽  
Pharmaceutical Journal ◽  
Significant Source ◽  
Comprehensive Review ◽  
Chemical Structures ◽  
Previous Review

Erythrina is a significant source of phytoconstituents. The aim of this review is to solicitude of classification, synthesis, and phytochemicals with biological activities of Erythrina. In our previous review on this genus (Hussain et. al., 2016a) fifteen species (Erythrina addisoniae, E. caribeae, E. indica, E. lattisima, E. melanacantha, E. mildbraedii, E. poeppigiama, E. stricta, E. subumbrans, E. veriagata, E. vespertilio, E. velutina, E. zeberi, E. zeyheri and E. americana) have been studied and 155 molecules with chemical structures were reported. A further comprehensive review was done upon continuation on the same genus and thirteen species (E. abyssinica, E. arborescens, E. berteroana, E. burttii, E. caffra, E. coralloids, E. crista-galli, E. fusca, E. herbaceae, E. lysistemon, E. mulungu, E. speciosa and E. tahitensis) of Erythrina have been studied and 127 compounds are reported as phytoconstituents with their chemical structure in this review. Erythrina crista-galli and E. lysistemon consist of highest number of chemical constituents. Bangladesh Pharmaceutical Journal 23(1): 65-77, 2020

scholarly journals Using Sentinel-2 Images to Estimate Topography, Tidal-Stage Lags and Exposure Periods over Large Intertidal Areas

2021 ◽  
Vol 13 (2) ◽  
pp. 320
Author(s):  
José P. Granadeiro ◽  
João Belo ◽  
Mohamed Henriques ◽  
João Catalão ◽  
Teresa Catry
Keyword(s):  
Large Scale ◽  
Exposure Period ◽  
Intertidal Area ◽  
Digital Elevation ◽  
Geographical Bias ◽  
Novel Method ◽  
Tidal Stage ◽  
Sentinel 2

Intertidal areas provide key ecosystem services but are declining worldwide. Digital elevation models (DEMs) are important tools to monitor the evolution of such areas. In this study, we aim at (i) estimating the intertidal topography based on an established pixel-wise algorithm, from Sentinel-2 MultiSpectral Instrument scenes, (ii) implementing a set of procedures to improve the quality of such estimation, and (iii) estimating the exposure period of the intertidal area of the Bijagós Archipelago, Guinea-Bissau. We first propose a four-parameter logistic regression to estimate intertidal topography. Afterwards, we develop a novel method to estimate tide-stage lags in the area covered by a Sentinel-2 scene to correct for geographical bias in topographic estimation resulting from differences in water height within each image. Our method searches for the minimum differences in height estimates obtained from rising and ebbing tides separately, enabling the estimation of cotidal lines. Tidal-stage differences estimated closely matched those published by official authorities. We re-estimated pixel heights from which we produced a model of intertidal exposure period. We obtained a high correlation between predicted and in-situ measurements of exposure period. We highlight the importance of remote sensing to deliver large-scale intertidal DEM and tide-stage data, with relevance for coastal safety, ecology and biodiversity conservation.

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