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

✍ Scribed by Jonas J. Forsman; Johan Wärnå; Dmitry Yu. Murzin; Reko Leino

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 976 KB
• Volume: 2009
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200900889

✦ Synopsis

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)