NDLI: Tin( IV) catalyzed D-galacturonic acid anomerization

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Rotondo, Archimede Casella, Girolamo A. Grasso, Giulia Rotondo, Enrico
Description	Author Affiliation: Rotondo A ( Dipartimento CICACF-Università di Messina-Salita Sperone, 31-98166 S.Agata-Messina, Italy. arotondo@unime.it)
Abstract	A comparative kinetic study of anomerization between the four main forms (α/β-pyranosides and α/β-furanosides) of D-galacturonic acid $(GalAH_{2},$ 1) and tin( IV) complexed D-galacturonate $([Sn(CH_{3})_{2}(GalA)(H_{2}O)_{2}],$ 2) in $D_{2}O,$ is reported. Important differences are shown by pD vs. mutarotation rate profiles of 1 and 2. Coordination, in fact, causes: i) a spectacular increase of the rate due to kinetic template assistance of the carboxylic tail holding the metal in close proximity to the reactive centre and ii) a change in the dependence of the rate on the pD . Entropic and enthalpic factors contribute to the huge activation energy decrease in 2. Anomerization rates of the complexed ligand are determined by 2D-EXSY cross-peak integration. Analysis of up to twelve direct and reverse rate constants in the pD range 7.0–2.5 evidences ring size memory , and at least one reaction path which bypasses the aldehydo open chain intermediate. Solvent oxygen atom incorporation into the ligand is, at pH 4.5, about ten fold faster when catalyzed by the metal, and proves that the metal-assisted nucleophilic attack of water on the anomeric carbon atom cannot significantly contribute to mutarotation rates that are thousands of times faster.
ISSN	14779226
Issue Number	5
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2008-02-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Hexuronic Acids Chemistry Tin Compounds Catalysis Kinetics Magnetic Resonance Spectroscopy Rotation Stereoisomerism Journal Article
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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