Sulfuric acid-catalyzed acetolysis of anomeric methyl 2,3,4,6-tetra-O-acetyl-d-mannopyranosides: kinetics and mechanism

Kaczmarek, Józef; Kaczyński, Zbigniew; Trumpakaj, Zygmunt; Szafranek, Janusz; Bogalecka, Magdalena; Lönnberg, Harri

doi:10.1016/s0008-6215(99)00308-0

Cited by 13 publications

(3 citation statements)

References 28 publications

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“…First‐order rate constants for exo activation of galacto ‐configured sugars are higher than for gluco ‐configured substrates 2g. In addition, the first‐order rate constant measured for endo activation of a manno ‐configured substrate is higher than for the gluco series 2h. This can be summarized with a relative order for the tendency to give an acetolysis reaction through an endo anomeric kinetically controlled mechanism, that is: manno > gluco > galacto , whereas the exo anomeric activation follows a different order ( galacto > manno > gluco ), which has recently been demonstrated to be mainly dictated by the less electron‐withdrawing power of axial over equatorial oxygens 23.…”

Section: Resultsmentioning

confidence: 91%

“…Indeed, they can be activated by a second acetylium ion to afford 1,1‐diacetate D and/or 1‐ O ‐Ac‐furanoside derivatives E . It has been shown that endo activation proceeds more rapidly, even if the relative rates of the two activation mechanisms are rather dependent on the sugar configuration 2h. Nevertheless, acetolysis is usually governed not by kinetic, but by thermodynamic conditions, thus giving products B in much higher yields than C , D , and/or E .…”

Section: Introductionmentioning

confidence: 99%

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Acetolysis of 6‐Deoxysugar Disaccharide Building Blocks: exo versus endo Activation

2008

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Two different protocols for the mild and selective acetolysis of 6-deoxysugar methyl disaccharides under thermodynamic or kinetic control have been developed. The structures of the disaccharides obtained depend on the protocol used and, in the kinetically controlled cases, on the 6-deoxysugar configuration and protecting group pattern too. The behavior of 6-deoxyhexose oligosaccharides of different series (rhamno,

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Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Acetolysis of 6‐Deoxysugar Disaccharide Building Blocks: exo versus endo Activation

2008

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“…The cleavage of an endocyclic C-O -bond has been observed in many reactions of pyranosides under anhydrous conditions. 34,35 As the environment in the active site of an enzyme may be hydrophobic, and hence resemble more organic solvent than water, reaction pathways observed in aqueous solutions may not apply to enzymatic reactions at all.…”

Section: Discussionmentioning

confidence: 99%

Hydrolytic decomposition of glycosides in aqueous acids

Mikkola¹,

Oivanen²

2008

Arkivoc

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A review is presented that collects the experimental results published on the acid catalyzed hydrolysis of alkyl and aryl pyranosides and furanosides over the last three decades. In aqueous acid, alkyl furanosides and pyranosides are hydrolysed via an oxocarbenium intermediate, which may be formed from the protonated substrate either by an exocyclic or endocyclic C-O bond cleavage. Both mechanisms lead eventually to the same products. Various methods have been used to distinguish between the pathways, and a lot of evidence exists to show that different pathways are followed depending on the structure of both the glycon moiety and the departing alcohol.

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Reaction Kinetics and Mechanism of Sulfuric Acid‐Catalyzed Acetolysis of Acylated Methyl L‐Ribofuranosides

et al. 2009

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The mechanism of the sulfuric acid‐catalyzed acetolysis of methyl 2,3,5‐tri‐O‐acetyl‐ and methyl 2,3,5‐tri‐O‐benzoyl‐L‐ribofuranosides and the accompanying anomerization of both the starting material and the 1,2,3,5‐tetra‐O‐acetyl‐ and 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐L‐ribofuranoses formed was investigated. The progress of the reactions was followed by 1H NMR spectroscopy and the rate constants for the reactions were determined for a proposed kinetic model. The role of H+ and Ac+ as the catalytically active species was clarified, proving that the anomerization of the acylated methyl furanosides is activated by protonation, while, on the contrary, the anomerization of the 1‐O‐acetyl ribofuranoses is activated by the acetyl cation. The anomerization of the acylated methyl furanosides was verified to be activated on the ring oxygen leading to endocyclic CO‐bond rupture while the 1‐O‐acetyl ribofuranoses are activated on the acetyloxy group on C(1) leading to exocyclic cleavage.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Sulfuric acid-catalyzed acetolysis of anomeric methyl 2,3,4,6-tetra-O-acetyl-d-mannopyranosides: kinetics and mechanism

Cited by 13 publications

References 28 publications

Acetolysis of 6‐Deoxysugar Disaccharide Building Blocks: exo versus endo Activation

Acetolysis of 6‐Deoxysugar Disaccharide Building Blocks: exo versus endo Activation

Hydrolytic decomposition of glycosides in aqueous acids

Reaction Kinetics and Mechanism of Sulfuric Acid‐Catalyzed Acetolysis of Acylated Methyl L‐Ribofuranosides

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