| Abstract
| - A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosylglycosides from furanoses is reported. The proposed methodology provides a new route for accessing2-deoxy-oligosaccharides. The procedure involves three reactions: Wittig−Horner olefination togive alkenyl sulfanyl derivatives, electrophilic iodine-induced cyclization to give phenyl 2-deoxy-2-iodo-1-thio-hexo-glycosides, and glycosylation. Protected furanoses 1, 3, and 6−11, which includeexamples of the four possible isomeric configurations of furanoses, were reacted with diphenylphenylsulfanylmethyl phosphine oxide to give the alkenyl sulfanyl derivatives 2, 4, and 12−16.The iodine-induced cyclization of these compounds afforded the phenyl 2-deoxy-2-iodo-1-thio-glycosides 18, 20, and 22−27 with practically complete regio- and stereoselectivity. Products of6-endo cyclization, in which the iodine at C-2 was in a cis relationship with the alkoxy at C-3, werealmost exclusively produced. Better yields were obtained for compounds with a ribo or xyloconfiguration than for compounds with other configurations. Compounds 18, 20, and 22−27 werefound to be efficient glycosyl donors in the glycosylation of cholesterol and glucopyranoside 29a,affording the corresponding 2-deoxy-2-iodo-glycosides and 2-deoxy-2-iodo-oligosaccharides with goodyields and stereoselectivities. The glycosydic bond in the major isomers was always trans to theiodine at C-2.
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