Facile Preparation of α-Glycosyl Iodides by In Situ Generated Aluminum Iodide: Straightforward Synthesis of Thio-, Seleno-, and <i>O</i>-glycosides from Unprotected Reducing Sugars
Streamlined Synthesis of Per-<i>O</i>-acetylated Sugars, Glycosyl Iodides, or Thioglycosides from Unprotected Reducing Sugars<sup>1</sup>
作者:Balaram Mukhopadhyay、K. P. Ravindranathan Kartha、David A. Russell、Robert A. Field
DOI:10.1021/jo048890e
日期:2004.10.1
Solvent-free per-O-acetylation of sugars with stoichiometric acetic anhydride and catalytic iodine proceeds in high yield (90-99%) to give exclusively pyranose products as anomeric mixtures. Without workup, subsequent anomeric substitution employing iodine in the presence of hexamethyldisilane (i.e., TMS-I generated in situ) gives the corresponding glycosyl iodides in 75-95% isolated yield. Alternatively, and without workup, further treatment with dimethyl disulfide or thiol (ethanethiol or thiocresol) gives anomerically pure thioglycosides in more than 75% overall yield.