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

Il presente lavoro è stato supportato da Vicerrectoría de Investigación y Estudios de Posgrado da BUAP, divulgazione della scienza e progetti n. REOY-NAT14, 15, 16-G. EMEL-NAT17. RMG grazie CONACyT (Messico) per la borsa di studio 417887.

1. reazione
<ol><li>Mettere in una cappa un pallone rotondo aperto 100 mL con 0,5 mol (29,8 mL) di acido acetico glaciale e aggiungere 0,051 mol (5,82 mL) di 3,5-dimethylpyridine e 5 mL di H2O2 (35%). Mantenere la reazione di miscela sotto costante agitazione magnetica, ad una temperatura interna di 80 ° C per 5 h.</li>
	<li>Dopo il tempo di reazione, raffreddare il pallone a 24 ° C con ghiaccio (do non esporre l'acido acetico di gas per il ghiaccio) e collegarlo a un'unità di distillazione sotto vuoto ad alta per 90-120 min per rimuovere l'eccesso di acido acetico. Attenzione: Non utilizzare materiale caldo. Attendere fino a quando il vetro raggiunge una temperatura gestibile. Questo eviterà anche vapori entrando parte superiore dell'unità di distillazione.</li>
	<li>Aggiungere acqua distillata acqua (10 mL) due volte a garantire la rimozione di qualsiasi traccia di acido acetico e di concentrare la miscela molto possibile.</li>
</ol>2. estrazione e regolazione basicità
<ol><li>Sciogliere in acqua bi-distillata prodotto viscoso e trasparente isolato e utilizzare un potenziometro per regolare il pH a 10 con puro solido Na2CO3.</li>
	<li>Posizionare con cura la soluzione in un imbuto separatore mL 250 ed estrarlo 5 volte con 250 mL di CHCl3 per migliorare il rendimento. Recuperare lo strato organico e asciugarlo sopra tinta Na2così4 per 30 min massimo, che conterrà il prodotto. Se necessario, estrarre nuovamente la fase acquosa con la quantità desiderata di CHCl3. Attenzione: CHCl3 può provocare sonnolenza e vertigini; maneggiare con cura e all'interno di una cappa aspirante.</li>
	<li>Rimuovere il solvente sotto pressione ridotta con un'unità di distillazione sotto vuoto ad alta, fino alla formazione di una polvere cristallina chiaro beige molto igroscopica (70%).</li>
</ol>3. della cristallizzazione
<ol><li>Sciogliere 4,3 g di polvere cristallina in 50 mL di etere etilico grado di freddo alta eseguita cromatografia liquida (HPLC). Filtro del vuoto la soluzione per rimuovere qualsiasi traccia di materiale solido di partenza o anche polvere. Versare il filtrato in un bicchiere di Petri, lasciandola a rallentare evaporare a 4 ° C in un frigorifero di laboratorio.</li>
	<li>Assicurarsi che dopo due giorni, si ottengono cristalli limpido incolore. Quindi misurare il punto di fusione, che dovrebbe essere nel range di K. 310-311</li>
</ol>4. analisi di 3,5-Lutidine N -ossido di disidratare
<ol><li>Rimuovere i cristalli che si formano, di forma prismatica e incolore, per decantazione dalle pareti del pallone per ulteriore analisi ai raggi x. Se non immediatamente utilizzato, è possibile mantenere i cristalli in etere etilico per evitare idratazione di cristallo.</li>
	<li>Sciogliere 0,010 g di 3,5-lutidine N -ossido di disidratare in 0,4 mL di CDCl3 per eseguire NMR H1 e C13 analisi per dimostrare l'efficacia della procedura.</li>
</ol>

<ol>
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Tutti gli autori non dichiarano alcun conflitto di interessi.

Il protocollo presentato qui è un metodo convenzionale per collegare un atomo di ossigeno all'atomo di azoto di 3,5-lutidine come un metodo di funzionalizzazione dei substrati. Questa tecnica è anche ben consolidata per produrre cristalli disidratati adatti di raggi x (Figura 5, le foto scattate con una fotocamera Sony DSC-HX300 Cyber-shot). Per quanto siamo preoccupati, non molti rapporti hanno descritto la produzione di tali cristalli16. Molti composti cresceranno cristalli id...

Al giorno d'oggi, gli scienziati di tutto il mondo hanno investito risorse nello sviluppo di nuove vie di sintesi per la funzionalizzazione dei gruppi aromatici, che sono conosciuti per la parte anteriore bassa reattività per aggiunta reazioni1,2, 3. Piridina, dove un atomo di azoto sostituisce un atomo di carbonio, presenta una reattività chimica simile analogico anelli è composto unicamente da atomi di carbonio3e subisce solitamente un meccanismo di sostituzione anziché aggiunta. N-ossidi si distinguono per la presenza di un legame di donatore tra azoto e ossigeno formata dalla sovrapposizione di nonbonding coppia di elettroni sull'azoto con un orbitale vuoto sul atomo di ossigeno3. In particolare, piridina N-ossido è basi di Lewis, perché loro frazione di N-O può agire come un donatore di elettroni, e si può combinare con acidi di Lewis, formando il corrispondente coppie acido-base di Lewis. Questa proprietà ha una conseguenza chimica essenziale, perché può aumentare la nucleofilicità degli acidi di Lewis verso potenziali elettrofili e quindi permettere loro di reagire in condizioni dove normalmente la reazione non si verificherebbe. Probabilmente l'uso più frequente di tali composti è nelle varie reazioni di ossidazione, dove agiscono come ossidanti4. Piridina N-ossidi e molti dei loro derivati funzionalizzati anello sono molecole ricorrenti di agenti biologicamente attivi e farmacologici5, e una distribuzione chiara spaziale di diversi strumenti spettroscopici è stata stabilita per alcuni di loro6,7. Nella ricerca sul collegamento di gruppi diversi per l'anello piridinico, gli scienziati hanno testato varie metodologie per produrre un metodo facile e convenzionale, dal isossazoline richiede una quantità catalitica di base quali DBU in ebollizione xilene per formare 6- sostituito-2-aminopyridine N-ossidi8,9. Una varietà di derivati della piridina sono stati convertiti in loro corrispondenti N-ossidi in presenza di una quantità catalitica di manganese tetrakis(2,6-diclorophenyl) porfirina e ammonio acetato CH2Cl2/CH3 CN8,10. Altri piridine sono ossidati a loro ossidi utilizzando H2O2 in presenza di quantità catalitiche di methyltrioxorhenium8,11, o con l'aggiunta di dimethyldioxirane in eccesso in CH2Cl2 a 0 ° C, che conduce al corrispondente N-ossidi8,12,13,14. Bis (trimetilsilile) perossido in presenza di trioxorhenium CH2Cl2 è stato utilizzato per la sintesi della piridina N-ossidi8,11. La sintesi di aminopiridina N-ossidi che coinvolge acilazione utilizzando (acido peroxomonosulfuric) di Caro è stato anche segnalato8. Tuttavia, la metodologia segnalato qui, e che utilizza parte della metodologia riportata da Ochiai1, fornisce risultati molto buoni con l'uso di reagenti più convenienti e accessibili, H2O2 e acido acetico glaciale. Questa pratica è più adatto ad uso nelle preparazioni su larga scala che agiscono sulle ammine terziarie, produce buone rese in una reazione che richiede solo 30% di perossido di idrogeno e acido acetico glaciale in una temperatura compresa tra 70-80 ° C e utilizza un processo di purificazione che è disponibile nella maggior parte dei laboratori di sintesi come la distillazione, senza l'uso del catalizzatore o più costosi reagenti1. La letteratura segnala che altre metodologie anche frequentemente coinvolgono tempo cornici da 10-24 h e temperature superiori a 100 ° C 4,8, e la resa di cristalli ben formati per analisi dei raggi x è segnalata raramente.
Reattivo, vari N -ossido derivati vengono utilizzati per attivare adeguatamente l'anello lutidine, in maniera elettrofila o nucleofila. Il fattore elettrofilo o nucleofilo risente i sostituenti. Con l'anello di piridina essendo i gruppi elettron-attrattori, il fattore principale è il nucleofilo caratteristica1. Il gratuito N-ossido composti sono raramente isolate come cristalli adatti per analisi di raggi x dovuto la carica delocalizzata sull'anello aromatico. Tuttavia, il fattore di solvatazione è fondamentale per stabilizzare la densità negativa dell' ossigeno15.

<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

La sintesi di 3,5-lutidine N -ossido di disidratare, 1, è stata realizzata nell'itinerario della sintesi dell'acido 2-ammino-piridina-3,5-dicarbossilico. Ochiai prima usato la metodologia per non-sostituiti piridine nel 1957 in un processo di 12 h, ma sono stato ottenuto senza cristalli adatto ai raggi x. L'anello sostituito utilizzato nella metodologia presentata qui chiaramente influenzato l'aggiunta di molecole d'acqua nell'unità asimmetrica, che conferisce una forza nucleofila diversa in 1. I raggi x cristallo adatto composto 1 era possibile dovuto la stabilizzazione della carica negativa nell'ossigeno dalla presenza di due molecole d'acqua dove gli atomi di idrogeno donano carica positiva sul ring; tali molecole di acqua servono bene per costruire un'interazione supramolecolare. Le molecole idratate potrebbero essere possibile per il sistema alcalino che si raggiunge regolando il pH a 10. D'importanza, il metile doppio sostituito con anello e un tempo di reazione di 5h, lo rende un metodo più versatile e con applicazioni chimiche più ampia per gli inserimenti futuri anello.

Il protocollo è essenzialmente un'estensione di Ochiai tecnica1. Tuttavia, vengono applicate le temperature più basse e meno tempo. Questo semplice metodo può essere utilizzato per ottenere un ligando versatile, che è un sostitutivo piridina N-ossido derivato. Per confermare la formazione di 1, NMR 1H e 13C analisi sono preferiti per testare l'efficacia della procedura.
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Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Qui, segnaliamo la sintesi e la cristallizzazione di 3,5-lutidine N -ossido di disidratare da un semplice protocollo che differisce dalla classica sintesi della piridina N-ossido. Questo protocollo utilizza materiale di partenza differente e comporta meno tempo di reazione per produrre una nuova struttura supramolecolare solvatato, che cristallizza sotto lenta evaporazione.

Sintesi, cristallizzazione e caratterizzazione spettroscopica di 3,5-Lutidine N-ossido di disidratare

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 Views.  Benemérita Universidad Autónoma de Puebla. Qui, segnaliamo la sintesi e la cristallizzazione di 3,5-lutidine N -ossido di disidratare da un semplice protocollo che differisce dalla classica sintesi della piridina N-ossido. Questo protocollo utilizza materiale di partenza differente e comporta meno tempo di reazione per produrre una nuova struttura supramolecolare solvatato, che cristallizza sotto lenta evaporazione.

Video: 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.

Sintesi e caratterizzazione di funzionalizzato metallo-organici quadri

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

Ricerca

Chimica

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.

Sintesi di indoxyl-glicosidi per il rilevamento di glicosidasi Attività

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.

La sintesi, caratterizzazione e reattività di una serie di rutenio<em&gt; N</em&gt; -triphos<sup&gt; Ph</sup&gt; Complessi

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.

Un protocollo per reazioni sicuro litiazione Utilizzando organolitio Reagenti

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.

One-pot assistita da microonde conversione di anomerica nitrato-esteri 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.

Reazioni a cascata enzimatica per la sintesi di Amino alcoli chirali da L-lisina

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.

Regioselettiva O- glicosilazione dei nucleosidi tramite il temporaneo 2', 3'-diolo protezione da boronico per la sintesi di disaccaride nucleosidi

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.

Costruzione efficiente di Drug-like Bispirocyclic ponteggi Via ORGANOCATALISI CICLOADDIZIONI di α-immino γ-lattoni e alchilidene pirazolone

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.

Una sintesi diretta, regiosesesesese ed economica di 3-Aroyl-N-idrossicco-5-nitroindoles di Cycloaddition di 4-Nitronidobenzee con alchinoni

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.

Sintesi dei Peptoidi a informazione e del loro autoassemblaggio covalente dinamico diretto in sequenza

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