Observations on the activation of methyl thioglycosides by iodine and its interhalogen compounds

Kartha, K. P.Ravindranathan, Cura, Peter, Aloui, Mahmoud, Readman, S. Kristy, Rutherford, Trevor J. and Field, Robert A. ORCID: https://orcid.org/0000-0001-8574-0275 (2000) Observations on the activation of methyl thioglycosides by iodine and its interhalogen compounds. Tetrahedron Asymmetry, 11 (2). pp. 581-593. ISSN 0957-4166

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Abstract

Treatment of 'armed' methyl thiogalactosides with iodine in the absence of an acceptor alcohol results in thioglycoside epimerisation, whereas there is no effect on the corresponding 'disarmed' methyl thioglycosides. In contrast, iodine-hexamethyldisilane (which generates iodotrimethylsilane in situ) brings about epimerisation of 'disarmed' thioglycosides, ultimately giving rise to the corresponding α-glycosyl iodides on extended exposure. Cross-over experiments show the former iodine-promoted epimerisation process to be intermolecular, whereas the latter iodine-hexamethyldisilane-promoted epimerisation is intramolecular. Treatment of the same methyl thiogalactosides with iodine monobromide gives rise to the thermodynamically favoured α-glycosyl bromides, whereas reaction with iodine monochloride initially gives the kinetic β-glycosyl chlorides, which slowly epimerise to the thermodynamic α-linked products. Differences in the outcome of thioglycoside activation by I-I, I-Br and I-Cl suggest there may be scope for influencing the stereochemical course of thioglycoside-based glycosylation reactions through careful choice of promoter. Copyright (C) 2000 Elsevier Science Ltd.

Item Type:	Article
Additional Information:	Funding Information: We thank the Wellcome Trust (grants: 042472 and 040331), the BBSRC/EPSRC, the Zeneca Strategic Research Fund and the University of St Andrews for financial support. We are grateful to Professor R. J. Ferrier for his interest in these studies and to Professor John Fothergill for assistance with mass spectrometry experiments.
Uncontrolled Keywords:	catalysis,physical and theoretical chemistry,organic chemistry,inorganic chemistry ,/dk/atira/pure/subjectarea/asjc/1500/1503
Faculty \ School:	Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	11 Sep 2024 09:30
Last Modified:	25 Sep 2024 18:08
URI:	https://ueaeprints.uea.ac.uk/id/eprint/96686
DOI:	10.1016/S0957-4166(99)00501-7

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