Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl4. Issue 44 (20th September 2013)

• Record Type: Journal Article
• Authors: Farrell, Mark; Zhou, Jian; Murphy, Paul V.
• Is Part Of: Chemistry. Volume 19:Issue 44(2013)
• Page Start: 14836
• Page End: 14851
• Publication Date: 2013-09-20
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201302572
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Chelation induced anomerisation is promoted when Lewis acids, such as TiCl₄ or SnCl₄, coordinate to the pyranose ring oxygen atom and another site, giving rise to endocyclic cleavage and isomerisation to the more stable anomer. In this research regiospecific site‐directed anomerisation is demonstrated. TiCl₄ (2.5 equiv) was employed to induce anomerisation of 15 glycosyl azide and disaccharide substrates of low reactivity, and high yields (&gt;75 %) and stereoselectivies (α/β&gt;9:1) were achieved. The examples included glucopyranuronate, galactopyranuronate and mannopyranuronate as well as N‐acetylated glucopyranuronate and galactopyranuronate derivatives. A disaccharide with the α1→4 linkage found in polygalacturonan was included. The use of benzoylated saccharides was found to be important in disaccharide anomerisation as attempts to isomerise related acetyl protected and 2, 3‐carbonate protected derivatives were not successful.</p> </abstract>