Stereoselective synthesis of 2-deoxy-2-iodo-glycosides from furanoses. A new route to 2-deoxy-glycosides and 2-deoxy-oligosaccharides of ribo and xylo configuration

Identifier:  imarina:6385130

Handle: https://hdl.handle.net/20.500.11797/imarina6385130

Authors:  Rodríguez, MA; Boutureira, O; Arnés, X; Matheu, MI; Díaz, Y; Castillón, S

Abstract:
A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosyl glycosides from furanoses is reported. The proposed methodology provides a new route for accessing 2-deoxy-oligosaccharides. The procedure involves three reactions: Wittig-Horner olefination to give 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 include examples of the four possible isomeric configurations of furanoses, were reacted with diphenyl phenylsulfanylmethyl 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 of 6-endo cyclization, in which the iodine at C-2 was in a cis relationship with the alkoxy at C-3, were almost exclusively produced. Better yields were obtained for compounds with a ribo or xylo configuration than for compounds with other configurations. Compounds 18, 20, and 22-27 were found 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 good yields and stereoselectivities. The glycosydic bond in the major isomers was always trans to the iodine at C-2. © 2005 American Chemical Society.