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Reaction Kinetics and Mechanism of Sulfuric Acid‐Catalyzed Acetolysis of Acylated Methyl L ‐Ribofuranosides
Author(s) -
Forsman Jonas J.,
Wärnå Johan,
Murzin Dmitry Yu.,
Leino Reko
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900889
Subject(s) - chemistry , protonation , catalysis , reaction rate constant , sulfuric acid , medicinal chemistry , kinetics , reaction mechanism , nuclear magnetic resonance spectroscopy , acid catalysis , stereochemistry , organic chemistry , ion , physics , quantum mechanics
Abstract 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 1 H 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)