Name: syntheses, crystallization, and spectroscopic characterization of 3,5-lutidine n-oxide dehydrate
Uploaded: 2018-04-24T14:00:00.000+00:00
Duration: 6 min 18 s
Description: Watch this Scientific Journal Video about Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate at JoVE.com

Die vorliegende Arbeit wurde unterstützt von Vicerrectoría de Investigación y Estudios de Posgrado von BUAP und Verbreitung der Wissenschaft Projekte Nr. REOY-NAT14, 15, 16-G. HEAŞ-NAT17. RMG Dank CONACyT (Mexiko) für Stipendium 417887.

1. Reaktion
<ol><li>In einer Dampfhaube eine geöffnete Runde 100 mL-Flasche mit 0,5 Mol (29,8 mL) Eisessig geben Sie und 0.051 Mol (5,82 mL) 3,5-Dimethylpyridine und 5 mL H2O2 (35 %). Halten Sie die Reaktion der Mischung unter ständigem Rühren magnetische, eine innere Temperatur von 80 ° C für 5 h.</li>
	<li>Kühlen Sie nach der Einwirkzeit die Küvette auf 24 ° C mit Eis (Do nicht aussetzen der Essigsäure auf das Eis Gase) und stecken Sie es auf eine hohe Vakuumdestillation Einheit für 90-120 min, überschüssige Essigsäure zu entfernen. Achtung: Verwenden Sie nicht heißes Material. Warten Sie, bis das Glas eine überschaubare Temperatur erreicht hat. Dies vermeidet auch Dämpfe in die Top der Destillation-Einheit.</li>
	<li>Fügen Sie destilliertes Wasser (10 mL) zweimal, um sicherzustellen, dass die entfernt von jeder Spur von Essigsäure und die Mischung zu konzentrieren viel wie möglich.</li>
</ol>(2) Basizität Anpassung und Extraktion
<ol><li>Isolierte zähflüssige und transparentere Produkt in Bi-distillated Wasser auflösen und ein Potentiometer zur Einstellung des pH-Wertes auf 10 mit pure solid Na2CO3verwenden.</li>
	<li>Legen Sie die Lösung in einem 250 mL-Trennung-Trichter vorsichtig und entpacken Sie es 5 Mal mit 250 mL Kchl3 , um den Ertrag zu verbessern. Wiederherstellen der organische Schicht und trocknen Sie es SO über solide Na24 30 Minuten maximal, die das Produkt enthält. Falls erforderlich, wieder extrahieren der wässrigen Phase mit der gewünschten Menge an Kchl3. Achtung: Kchl3 können Schläfrigkeit und Benommenheit verursachen; behandeln Sie mit Sorgfalt und in einer Dampfhaube.</li>
	<li>Entfernen Sie das Lösungsmittel unter vermindertem Druck mit einem hohen Vakuum-Destillation bis zur Bildung des ein sehr hygroskopisch klar Beige, kristallines Pulver (70 %).</li>
</ol>3. die Kristallisation
<ol><li>4,3 g kristallines Pulver in 50 mL kalten hohe durchgeführten Flüssigkeitschromatographie (HPLC) Grade Diethylether auflösen. Vakuum-Filter die Lösung für jede Spur von soliden Ausgangsmaterial oder sogar Staub zu entfernen. Das Filtrat in ein Glas Petrischale Gießen, so dass es zu langsam verdunsten bei 4 ° C in einem Labor-Kühlschrank.</li>
	<li>Stellen Sie sicher, dass nach zwei Tagen, klare farblose Kristalle gewonnen werden. Dann Messen Sie den Schmelzpunkt, die im Bereich von 310-311 K. sein sollte</li>
</ol>4. Analyse der 3,5-Lutidine N -oxid gelief
<ol><li>Entfernen Sie die Kristalle, die prismatische Form und farblos, durch Dekantieren von der Küvette Wänden für weitere röntgenstrahlanalyse gebildet werden. Wenn nicht sofort verwendet, halten Sie die Kristalle in Diethylether, Kristall Flüssigkeitszufuhr zu vermeiden.</li>
	<li>Auflösen von 0,010 g 3,5-Lutidine N -oxid entwässern in 0,4 mL CDCl3 , NMR H1 und C-13 -Analyse, beweisen die Wirksamkeit des Verfahrens durchzuführen.</li>
</ol>

<ol>
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Alle Autoren erklären keinen Interessenskonflikt.

Das Protokoll hier vorgestellten ist eine konventionelle Methode, um ein Sauerstoffatom an das Stickstoffatom des 3,5-Lutidine als eine Methode der Funktionalisierung der Substrate zu verknüpfen. Diese Technik ist auch etablierte Röntgen geeignet dehydriert Kristalle (Abbildung 5, fotografiert mit einer Sony DSC-HX300 Cyber-Shot-Kamera) zu liefern. Soweit wir betroffen sind, haben nicht viele Berichte die Produktion solcher Kristalle16beschrieben. Viele Verbindungen wachsen idea...

Heute haben Wissenschaftler auf der ganzen Welt Ressourcen in die Entwicklung neuer Synthesewege für die Funktionalisierung von aromatischen Gruppen, investiert die Hinzufügung Reaktionen1,2für niedrige Reaktivität Front bekannt sind, 3. Pyridin, wo ein Stickstoffatom ein Kohlenstoffatom ersetzt, stellt eine ähnliche chemische Reaktivität auf Analog, die ausschließlich aus Kohlenstoff-Atomen3Ringe komponiert, und er erfährt in der Regel eine Substitution Mechanismus als Ergänzung. N-Oxide zeichnen sich durch die Anwesenheit einer Spender-Bindung zwischen Stickstoff und Sauerstoff durch die Überlappung der nonbonding Elektronenpaar am Stickstoff mit einer leeren Orbital auf dem Sauerstoff-Atom-3gebildet. Vor allem, Pyridin N-Oxide sind Lewis-Basen, weil ihre N-O Glyko-kann als ein Elektron Spender handeln, und sie möglicherweise mit Lewis-Säuren bilden die entsprechenden Lewis-Säure-Basen-Paare verbinden. Diese Eigenschaft hat eine wesentliche chemische Folge, weil es kann die Nucleophilicity von Lewis-Säuren gegenüber potenziellen Electrophiles erhöhen und somit, unter Bedingungen zu reagieren ermöglichen, wo würde normalerweise die Reaktion nicht auftreten. Wahrscheinlich ist die häufigste Verwendung solcher Verbindungen in verschiedenen Oxidationsreaktionen, wo sie als Oxidationsmittel4handeln. Pyridin- N-Oxide und vieler ihrer Ring funktionalisiert Derivate sind wiederkehrende Moleküle von biologisch aktiven und pharmakologische Wirkstoffe5und eine klare räumliche Verteilung durch verschiedene spektroskopische Werkzeuge wurde eingerichtet für einige von ihnen6,7. In der Forschung über die Pyridin Ring verschiedene Gruppen zuweisen haben Wissenschaftler testeten verschiedene Methoden um eine einfache und konventionelle Methode zu produzieren, da Isoxazolines eine katalytische Menge an Base wie DBU erfordert in siedendem Xylol zu bilden 6- ersetzt-2-Aminopyridine N-Oxide8,9. Eine Vielzahl von Pyridin-Derivate wurden umgewandelt in ihre entsprechenden N-Oxide in der Gegenwart eine katalytische Menge an Mangan tetrakis(2,6-diclorophenyl) Porphyrin und Ammonium-Acetat CH2Cl2/CH3 CN8,10. Andere Pyridines sind auf ihre Oxide mit H2O2 in Anwesenheit von katalytische Mengen von Methyltrioxorhenium8,11, oder durch die Zugabe von überschüssigen Dimethyldioxirane in CH2Cl2 oxidiert. bei 0 ° C, wodurch die entsprechenden N-Oxide8,12,13,14. BIZ (Trimethylsilyl) Wasserstoffperoxid in Gegenwart von Trioxorhenium in CH2Cl2 wird für die Synthese von Pyridin- N-Oxide8,11. Die Synthese von Aminopyridine N-Oxide mit Acylation mit Carosche Säure (Peroxomonosulfuric Säure) auch wurde berichtet,8. Dennoch, die Methodik hier berichtet, und die Teil der Methodik von Ochiai1, berichtet verwendet liefert sehr gute Ergebnisse mit dem Einsatz von billiger und zugänglich Reagenzien, H2O2 und Eisessig. Diese Praxis ist besser geeignet für den Einsatz in großem Maßstab Vorbereitungen, die auf tertiäre Amine wirken, es produziert gute Erträge in einer Reaktion, die nur 30 % Wasserstoffperoxid erfordert und Eisessig in eine Temperatur zwischen 70-80 ° C und es nutzt einen Reinigungsprozess in den meisten Synthese Laboratorien wie Destillation, ohne den Einsatz von Katalysatoren oder teurer Reagenzien1verfügbar ist. Die Literatur berichtet, dass andere Methoden häufig auch Fristen von 10-24 h und Temperaturen über 100 ° C 4,8 beinhalten, und der Ertrag von gut ausgebildeten Kristallen für Röntgen-Analysen wird selten berichtet.
Reaktiv, werden verschiedene N -oxid-Derivate verwendet, um angemessen die Lutidine Ring auf einer nukleophilen oder elektrophiler Weise aktivieren. Der nukleophilen oder elektrophiler Faktor betrifft die Substituenten. Mit dem Pyridin Ring wird die Aberkennung der Elektron-Gruppen ist der Hauptfaktor der nukleophilen charakteristischen1. Die kostenlose N-oxid Verbindungen sind selten isoliert als geeignete Kristalle für röntgenstrahlanalyse durch delokalisierte Ladung in den aromatischen Ring. Die Solvatation Faktor ist jedoch entscheidend für die negative Dichte der Sauerstoff15zu stabilisieren.

<table><tbody><tr><td>3,5-lutidine</td><td>Sigma-Aldrich</td><td>L4206-500ML</td><td></td></tr><tr><td>Glacial acetic acid</td><td>Fermont</td><td>3015</td><td></td></tr><tr><td>Hidrogen peroxide (35%)</td><td>Sigma-Aldrich</td><td>349887-500ML</td><td></td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3&lt;/sub&gt; anhydrous</td><td>Productos Qu&amp;iacute;micos Monterrey</td><td>1792</td><td></td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; anhydrous</td><td>Alfa reactivos</td><td>25051-C</td><td></td></tr><tr><td>CHCl&lt;sub&gt;3&lt;/sub&gt;</td><td>Fermont</td><td>6205</td><td></td></tr><tr><td>Ethyl eter</td><td>Mercury Chemist</td><td>QME0309</td><td></td></tr><tr><td>Distilled water</td><td>Comercializadora Qu&amp;iacute;mica Poblana</td><td>not-existent</td><td></td></tr></tbody></table>

syntheses, crystallization, and spectroscopic characterization of 3,5-lutidine n-oxide dehydrate

Die Synthese von 3,5-Lutidine N -Oxid zu entwässern, 1, wurde in der Synthese von 2-amino-Pyridin-3,5-dicarboxylic Säure erreicht. Ochiai zuerst die Methodik für nicht ersetzt Pyridines im Jahre 1957 in einem 12 h-Prozess, aber kein Röntgen geeignet Kristalle stammen. Die substituierte Ring verwendet, in der hier vorgestellten Methodik beeinflusst deutlich die Zugabe von Wasser-Moleküle in die asymmetrische Einheit, die eine unterschiedliche nukleophilen Stärke 1verleiht. Die x-ray geeignet Kristall zusammengesetzte 1 war möglich, da die Stabilisierung der negativen Ladung in der Sauerstoff durch die Anwesenheit von zwei Wassermolekülen wo Spenden die Wasserstoffatome positiven Ladung in den Ring; Diese Wassermoleküle auch dazu dienen, eine supramolekulare Interaktion zu konstruieren. Die hydratisierten Moleküle können für das alkalische System möglich, die erreicht wird durch Einstellen des pH-Werts um 10. Wichtig ist, die doppelte Methyl ersetzt, Ring und einer Reaktionszeit von 5 h, macht es eine vielseitigere Methode und mit breiteren chemische Anwendungen für zukünftige Ring Einfügungen.

Das Protokoll ist im Wesentlichen eine Erweiterung des Ochiai Technik1. Allerdings gelten niedrigere Temperatur und weniger Zeit. Diese einfache Methode lässt sich eine vielseitige Liganden zu erhalten, eine ersetzte Pyridin- N-oxid Ableitung. Um die Bildung von 1zu bestätigen, werden NMR 1H und 13C Analyse bevorzugt, um die Wirksamkeit des Verfahrens prüfen.
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Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Hier berichten wir, der Synthese und Kristallisation von 3,5-Lutidine N -Oxid zu entwässern, durch ein einfaches Protokoll, das unterscheidet sich von der klassischen Synthese von Pyridin- N-oxid. Dieses Protokoll nutzt verschiedene Ausgangsmaterial und beinhaltet weniger Reaktionszeit auf eine neue SOLVATISIERTE supramolekulare Struktur ergeben, der unter langsame Verdunstung kristallisiert.

Synthesen, Kristallisation und spektroskopische Charakterisierung von 3,5-Lutidine- N-Oxid zu entwässern

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the ...

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Chemistry

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

8.3K Aufrufe.  Benemérita Universidad Autónoma de Puebla. Hier berichten wir, der Synthese und Kristallisation von 3,5-Lutidine N -Oxid zu entwässern, durch ein einfaches Protokoll, das unterscheidet sich von der klassischen Synthese von Pyridin- N-oxid. Dieses Protokoll nutzt verschiedene Ausgangsmaterial und beinhaltet weniger Reaktionszeit auf eine neue SOLVATISIERTE supramolekulare Struktur ergeben, der unter langsame Verdunstung kristallisiert.

Serie: Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Synthese und Charakterisierung von funktionalisierten Metall-organische Gerüste

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Forschung

Chemie

Synthesis of Indoxyl-glycosides for Detection of Glycosidase Activities

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are rapidly oxidized, for example by atmospheric oxygen, to indigo type dyes. This reaction enables fast and easy screening in vivo without isolation or purification of enzymes, as well as rapid tests on agar plates or in solution (e.g., blue-white screening, micro-wells) and is used in biochemistry, histochemistry, bacteriology and molecular biology. Unfortunately the synthesis of such substrates proved to be difficult, due to various side reactions and the low reactivity of the indoxyl hydroxyl function. Especially for glucose type structures low yields were observed. Our novel approach employs indoxylic acid ester as key intermediates. Indoxylic acid esters with varied substitution patterns were prepared on scalable pathways. Phase transfer glycosylations with those acceptors and peracetylated glycosyl halides can be performed under common conditions in high yields. Ester cleavage and subsequent mild silver mediated glycosylation yields the peracetylated indoxyl glycosides in high yields. Finally deprotection is performed according to Zempl&#233;n.

Indoxyl glycosides are well-established and widely used tools for enzyme screening and enzyme activity monitoring. Especially for glucose type structures previous syntheses proved to be challenging and low yielding. Our novel approach employs indoxylic acid esters as precious intermediates to yield a considerable number of indoxyl glycosides in good yields.

Synthese von Indoxyl-Glykoside zum Nachweis von Glycosidase Aktivitäten

Indoxyl glycosides proved to be valuable and versatile tools for monitoring glycosidase activities. Indoxyls are released by enzymatic hydrolysis and are ...

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the hydroxylmethylene phosphine precursor with ammonia in methanol under a nitrogen atmosphere. The N-triphosPh ligand precipitates from the solution after approximately 1 hr of reflux and can be isolated analytically pure via simple cannula filtration procedure under nitrogen. Reaction of the N-triphosPh ligand with [Ru3(CO)12] under reflux affords a deep red solution that show evolution of CO gas on ligand complexation. Orange crystals of the complex [Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2) were isolated on cooling to RT. The 31P{1H} NMR spectrum showed a characteristic single peak at lower frequency compared to the free ligand. Reaction of a toluene solution of complex 2 with oxygen resulted in the instantaneous precipitation of the carbonate complex [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) as an air stable orange solid. Subsequent hydrogenation of 3 under 15 bar of hydrogen in a high-pressure reactor gave the dihydride complex [RuH2(CO){N(CH2PPh2)3}-&#954;3P] (4), which was fully characterized by X-ray crystallography and NMR spectroscopy. Complexes 3 and 4 are potentially useful catalyst precursors for a range of hydrogenation reactions, including biomass-derived products such as levulinic acid (LA). Complex 4 was found to cleanly react with LA in the presence of the proton source additive NH4PF6 to give [Ru(CO){N(CH2PPh2)3}-&#954;3P{CH3CO(CH2)2CO2H}-&#954;2O](PF6) (6).

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium phosphine complexes are widely used for homogeneous catalytic reactions such as hydrogenations. The synthesis of a series of novel tridentate ruthenium complexes bearing the N-triphos ligand N(CH2PPh2)3 is reported. Additionally, the stoichiometric reaction of a dihydride Ru&#8211;N-triphos complex with levulinic acid is described.

Die Synthese, Charakterisierung und Reaktivität von einer Serie von Ruthenium<em&gt; N</em&gt; -triphos<sup&gt; Ph</sup&gt; Komplexe

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Ein Protokoll für sichere Lithiierungen Mit Organolithiumreagentien

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate glycosyl donor. Following azido-nitration of a glycal, the product 2-azido-1-nitrate ester can be hydrolyzed under microwave-assisted irradiation. This transformation is usually achieved using strongly nucleophilic reagents and extended reaction times. Microwave irradiation induces hydrolysis, in the absence of reagents, with short reaction times. Following denitration, the intermediate anomeric alcohol is converted, in the same pot, to the corresponding 2-azido-1-trichloroacetimidate.

A 2-azido-1-nitrate-ester can be converted to the corresponding 2-azido-1-trichloroacetimidate in a one-pot procedure. The goal of the manuscript is to demonstrate utility of the microwave reactor in carbohydrate synthesis.

Ein-Topf Mikrowellen-gestützte Umwandlung des Anomeric Nitrat-Ester und Trichloroacetimidates

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate ...

Enzymatic Cascade Reactions for the Synthesis of Chiral Amino Alcohols from L-lysine

Amino alcohols are versatile compounds with a wide range of applications. For instance, they have been used as chiral scaffolds in organic synthesis. Their synthesis by conventional organic chemistry often requires tedious multi-step synthesis processes, with difficult control of the stereochemical outcome. We present a protocol to enzymatically synthetize amino alcohols starting from the readily available L-lysine in 48 h. This protocol combines two chemical reactions that are very difficult to conduct by conventional organic synthesis. In the first step, the regio- and diastereoselective oxidation of an unactivated C-H bond of the lysine side-chain is catalyzed by a dioxygenase; a second regio- and diastereoselective oxidation catalyzed by a regiodivergent dioxygenase can lead to the formation of the 1,2-diols. In the last step, the carboxylic group of the alpha amino acid is cleaved by a pyridoxal-phosphate (PLP) decarboxylase (DC). This decarboxylative step only affects the alpha carbon of the amino acid, retaining the hydroxy-substituted stereogenic center in a beta/gamma position. The resulting amino alcohols are therefore optically enriched. The protocol was successfully applied to the semipreparative-scale synthesis of four amino alcohols. Monitoring of the reactions was conducted by high performance liquid chromatography (HPLC) after derivatization by 1-fluoro-2,4-dinitrobenzene. Straightforward purification by solid-phase extraction (SPE) afforded the amino alcohols with excellent yields (93% to &#62;95%).

Chiral amino alcohols are versatile molecules for use as scaffolds in organic synthesis. Starting from L-lysine, we synthesize amino alcohols by an enzymatic cascade reaction combining diastereoselective C-H oxidation catalyzed by dioxygenase followed by cleavage of the carboxylic acid moiety of the corresponding hydroxyl amino acid by a decarboxylase.

Enzymatische Kaskade Reaktionen für die Synthese von chirale Alkohole Aminosäure L-Lysin

Amino alcohols are versatile compounds with a wide range of applications. For instance, they have been used as chiral scaffolds in organic synthesis. ...

Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

Disaccharide nucleosides, which consist of disaccharide and nucleobase moieties, have been known as a valuable group of natural products having multifarious bioactivities. Although chemical O-glycosylation is a commonly beneficial strategy to synthesize disaccharide nucleosides, the preparation of substrates such as glycosyl donors and acceptors requires&#160;tedious protecting&#160;group manipulations and a purification at each synthetic step. Meanwhile, several research groups have reported that boronic and borinic esters serve as a protecting or activating group of carbohydrate derivatives to achieve the regio- and/or stereoselective acylation, alkylation, silylation, and glycosylation. In this article, we demonstrate the procedure for the regioselective O-glycosylation of unprotected ribonucleosides utilizing boronic acid. The esterification of 2&#39;,3&#39;-diol of ribonucleosides with boronic acid makes the temporary protection of diol, and, following O-glycosylation with a glycosyl donor in the presence of p-toluenesulfenyl chloride and silver triflate, permits the regioselective reaction of the 5&#39;-hydroxyl group to afford the disaccharide nucleosides. This method could be applied to various nucleosides, such as guanosine, adenosine, cytidine, uridine, 5-metyluridine, and 5-fluorouridine. This article and the accompanying video represent&#160;useful (visual) information for the O-glycosylation of unprotected nucleosides and their analogs for the synthesis of not only disaccharide nucleosides, but also a variety of biologically relevant derivatives.

Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

Here, we present protocols for the synthesis of disaccharide nucleosides by the regioselective O-glycosylation of ribonucleosides via a temporary protection of their 2&#39;,3&#39;-diol moieties utilizing a cyclic boronic ester. This method applies to several unprotected nucleosides such as adenosine, guanosine, cytidine, uridine, 5-methyluridine, and 5-fluorouridine to give corresponding disaccharide nucleosides.

Regioselective O- Glykosylierung Nukleoside über die temporäre 2', 3'-Diol Schutz durch eine Boronic Ester für die Synthese von Disaccharid Nukleosiden

Disaccharide nucleosides, which consist of disaccharide and nucleobase moieties, have been known as a valuable group of natural products having ...

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of &#945;-Imino &#947;-Lactones and Alkylidene Pyrazolones

Bispirocyclic scaffolds are one of the important structural subunits in many natural products that exhibit diverse and attractive biological activities. Recently, we have developed an efficient organocatalytic strategy, which provides facile access to a variety of enantiomerically enriched bispiro[&#947;-butyrolactone-pyrrolidin-4,4&#39;-pyrazolone] skeletons. In this paper, we demonstrate a detailed protocol for the asymmetric synthesis of drug-like bispirocyclic compounds with two spirocyclic carbon centers via an organocatyltic 1,3-dipolar cycloaddition reaction. Spirocyclization synthons &#945;-imino &#947;-lactones and alkylidene pyrazolones are prepared first, which are then subjected to a cycloaddition reaction in the presence of a bifunctional squaramide organocatalyst to afford the desired bispirocycles in high yields and excellent stereoselectivities. Chiral high-performance liquid chromatography (HPLC) is carried out to determine the enantiomeric purity of the products, and the d.r. value is examined by proton nuclear magnetic resonance (1H NMR). The absolute configuration of the product is assigned according to an X-ray crystallographic analysis. This synthetic strategy allows scientists to prepare a diversity of bispirocyclic scaffolds in high yields and excellent diastereo- and enantioselectivities.

Enantiomerically enriched bispiro[&#947;-butyrolactone-pyrrolidin-4,4&#39;-pyrazolone] skeletons are asymmetrically synthesized through a simple organocatalytic 1,3-dipolar cycloaddition reaction.

Energieeffizientes bauen Drogen wie Bispirocyclic Gerüste über Organocatalytic Cycloadditions von α-Imino γ-Lactone und Alkylidene Pyrazolones

Bispirocyclic scaffolds are one of the important structural subunits in many natural products that exhibit diverse and attractive biological activities. ...

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ketones. The reactions were carried out achieving indoles without any catalyst and with excellent regioselectivity. No traces of 2-aroylindole products were detected. Working with 4-nitronitrosobenzene as starting material, the 3-aroyl-N-hydroxy-5-nitroindole products precipitated from the reaction mixtures and were isolated by filtration without any further purification technique. Differently from the corresponding N-hydroxy-3-aryl indoles that, spontaneously in solution, give dehydrodimerization products, the N-hydroxy-3-aroyl indoles are stable and no dimerization compounds were observed.

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

3-Aroyl-N-hydroxy-5-nitroindoles were synthesized by cycloaddition of 4-nitronitrosobenzene with a conjugated terminal alkynone in a one-step thermal procedure. Preparation of the nitrosoarene and of the alkynones were adequately reported and respectively through oxidation procedures on the corresponding aniline and on the alkynol.

Eine direkte, regioselektive und atomökonomische Synthesevon 3-Aroyl-N-Hydroxy-5-Nitroindolen durch Cycloaddition von 4-Nitronitrosobenzol mit Alkynonen

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ...

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

This protocol presents the use of Lewis acidic multi-role reagents to circumvent kinetic trapping observed during the self-assembly of information-encoded oligomeric strands mediated by paired dynamic covalent interactions in a manner mimicking the thermal cycling commonly employed for the self-assembly of complementary nucleic acid sequences. Primary amine monomers bearing aldehyde and amine pendant moieties are functionalized with orthogonal protecting groups for use as dynamic covalent reactant pairs. Using a modified automated peptide synthesizer, the primary amine monomers are encoded into oligo(peptoid) strands through solid-phase submonomer synthesis. Upon purification by high-performance liquid chromatography (HPLC) and characterization by electrospray ionization mass spectrometry (ESI-MS), sequence-specific oligomers are subjected to high-loading of a Lewis acidic rare-earth metal triflate which both deprotects the aldehyde moieties and affects the reactant pair equilibrium such that strands completely dissociate. Subsequently, a fraction of the Lewis acid is extracted, enabling annealing of complementary sequence-specific strands to form information-encoded molecular ladders characterized by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The simple procedure outlined in this report circumvents kinetic traps commonly experienced in the field of dynamic covalent assembly and serves as a platform for the future design of robust, complex architectures.

A protocol is presented for the synthesis of information-encoded peptoid oligomers and for the sequence-directed self-assembly of these peptoids into molecular ladders using amines and aldehydes as dynamic covalent reactant pairs and Lewis acidic rare-earth metal triflates as multi-role reagents.

Synthese von informationstragenden Peptoiden und deren sequenzgesteuerter dynamischer kovalenter Selbstmontage

This protocol presents the use of Lewis acidic multi-role reagents to circumvent kinetic trapping observed during the self-assembly of information-encoded ...