Über das ω‐Oxymethyl‐furfurol als Ursache einiger Farbreaktionen der Hexosen)

Ekenstein, W. Alberda van; Blanksma, J. J.

doi:10.1002/cber.191004302202

Cited by 42 publications

(8 citation statements)

References 11 publications

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“…Nevertheless, the results with the Omethyl derivatives and with the O-phosphate derivatives support a mechanism which involves: (1) initial cleavage of the glycosyl bond, (2) subsequent attack of the 2'-oxygen at C-5' with displacement of the protonated phosphate or protonated methoxyl group to give a five-membered ring, and (3) dehydration in the strong acid milieu to give furfural which in turn reacts with orcinol to give the green color. The ease of conversion into furfural of compounds with 2,5-anhydro rings is well known (Cifonelli et al, 1955;Ekenstein and Blanksma, 1910). Such a mechanism would explain the slow reaction of 2'-0-methylated derivatives which have to be demethylated to acquire the essential free 2'-hydroxyl group.…”

Section: Discussionmentioning

confidence: 99%

The preparation and properties of O-methylated adenosine derivatives

Gin¹,

Dekker²

1968

Biochemistry

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By reacting diazomethane with adenosine in a partially aqueous medium, 2'-O-methyladenosine, 3'-O-methyladenosine, 5'-O-methyladenosine, and 2',-3'-di-O-methyladenosine have been prepared in 38, 11, 1.5, and 3.5% yields, respectively. These yields are in general accord with the known mechanism of action of diazomethane and with the acidities of the individual hydroxyl groups of adenosine as determined by ion-exchange chromatography of the O-methylated derivatives on Dowex 1 (OH-) columns, i.e., the more acidic the hydroxyl groups, the greater the extent of methylation. Replacement of the 2'and/or 3'-hydroxyl group of adenosine by a methoxyl group slightly stabilized the glycosyl bond to acid-catalyzed hydrolysis. For 0.1 n HC1, 97.5°, the following first-order rate constants were determined: adenosine, 10 X 10-4 sec-1; 5'-0-^^/hile it is now clearly established that both tand rRNAs are frequently methylated at the 2'-oxygen of some of their ribose residues (Smith and Dunn, 1959; Singh and Lane, 1964a,b;Hall, 1964), our knowledge of the chemical behavior and biological significance of 2'-0-methyl nucleoside residues is, at best, fragmentary.Recent progress in methylating procedures (Broom and Robins, 1965; Khwaja and Robins, 1966) has made possible selective O methylation of adenosine and cytidine. Using the Broom and Robins (1965) procedure which employs diazomethane in aqueous dimethoxyethane, we have obtained on reaction of adenosine: 3'-O-methyladenosine, 5'-O-methyladenosine, and 2',-3'-di-O-methyladenosine in addition to the 2 '-0methyladenosine initially reported (Broom and Robins, 1965). These methylated adenosines can be readily separated by a combination of cellulose and anion-exchange chromatography making use, in the case of the latter technique, of the variation in acidity of the remaining hydroxyl groups of the derivatized adenosines (Dekker, 1965). In this paper we describe the isolation and properties of several methylated adenosines and their behavior toward (1) acid hydrolysis, (2) enzymatic deamination, and (3) the orcinol reaction.The preparation of 3'-O-methyladenosine has also been accomplished by the coupling of the appropriate

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Section: Discussionmentioning

confidence: 99%

The preparation and properties of O-methylated adenosine derivatives

Gin¹,

Dekker²

1968

Biochemistry

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“…Furanic compounds have been observed in the acid dehydration of 2,5-anhydro sugars. 88b, 95 The dehydration of 2,5-anhydro-D-mannose to HMF was observed to proceed slower than when starting from fructose. On the basis of this observation chitose was excluded as a likely intermediate in the dehydration of fructose to HMF.…”

Section: Neutral Monomeric Sugarsmentioning

confidence: 98%

Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources

et al. 2013

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“…[23] TheE SI-MS spectrum of the 158 gmol À1 compound (compound 3i n Scheme 1) suggests that it is the dehydrogenation producto f compound 1, i.e.,o ne of the 2,5-anydro-hexosest hat have also been implicated in fructose dehydration. [34][35][36][37] It is likely that this dehydrogenated product is as ide-producta ssociated with the stoichiometric oxidationofthe alcohol groups by the tungsten oxide catalyst into the stable dehydrogenated side-product. In keepingw ith this, we observed the yellow WO 3 sample turn blue, indicative of the reduction of W 6 + to W 5 + .W es peculate that this product is relatively stable, whereas com-pound2will be rapidly dehydrated to HMF by HCl.…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

Dehydration of Glucose to 5‐Hydroxymethylfurfural Using Nb‐doped Tungstite

Yue

Pidko

et al. 2016

ChemSusChem

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Dehydration of glucose to 5‐hydroxymethylfurfural (HMF) remains a significant problem in the context of the valorization of lignocellulosic biomass. Hydrolysis of WCl6 and NbCl5 leads to precipitation of Nb‐containing tungstite (WO3⋅H2O) at low Nb content and mixtures of tungstite and niobic acid at higher Nb content. Tungstite is a promising catalyst for the dehydration of glucose to HMF. Compared with Nb2O5, fewer by‐products are formed because of the low Brønsted acidity of the (mixed) oxides. In water, an optimum yield of HMF was obtained for Nb–W oxides with low Nb content owing to balanced Lewis and Brønsted acidity. In THF/water, the strong Lewis acidity and weak Brønsted acidity caused the reaction to proceed through isomerization to fructose and dehydration of fructose to a partially dehydrated intermediate, which was identified by LC‐ESI‐MS. The addition of HCl to the reaction mixture resulted in rapid dehydration of this intermediate to HMF. The HMF yield obtained in this way was approximately 56 % for all tungstite catalysts. Density functional theory calculations show that the Lewis acid centers on the tungstite surface can isomerize glucose into fructose. Substitution of W by Nb lowers the overall activation barrier for glucose isomerization by stabilizing the deprotonated glucose adsorbate.

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Über das ω‐Oxymethyl‐furfurol als Ursache einiger Farbreaktionen der Hexosen)

Cited by 42 publications

References 11 publications

The preparation and properties of O-methylated adenosine derivatives

The preparation and properties of O-methylated adenosine derivatives

Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources

Dehydration of Glucose to 5‐Hydroxymethylfurfural Using Nb‐doped Tungstite

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