PAPER	Synthesis 2002: 1721-1727 DOI: 10.1055/s-2002-33641
© Georg Thieme Verlag Stuttgart · New York
Regioselective Conversion of Primary Alcohols into Iodides in Unprotected Methyl Furanosides and Pyranosides
Philip R. Skaanderup, Carina Storm Poulsen, Lene Hyldtoft, Malene R. Jørgensen, Robert Madsen*
Department of Chemistry, Building 201, Technical University of Denmark, 2800 Lyngby, Denmark Fax: +4545933968; e-Mail: rm@kemi.dtu.dk;
Received 4 April 2002

Abstract

Two methods are described for the regioselective displacement of the primary hydroxy group in methyl glycosides with iodide. The first method is a modification of a literature procedure employing triphenylphosphine and iodine, where purification has been carried out on a reverse phase column in order to efficiently separate the desired iodoglycosides from triphenylphosphine oxide. The second method employs a new procedure using sulfonylation in pyridine with sterically hindered 2,4,6-trichloro- and 2,4,6-tribromobenzenesulfonyl chloride. The sulfonates thus formed are effective leaving groups and substitution with iodide can be carried out in a one-pot process. Protection of the iodoglycosides is also described either by benzylation with benzyl trichloroacetimidate or silylation­ with triethylsilyl chloride.

Key words

carbohydrates - halogenation - regioselectivity - substitution - sulfonates