Stereospecific synthesis of 1,2-cis glycosides by allyl-mediated intramolecular aglycon delivery. 2. The use of glycosyl fluorides

[GRAPHICS] Stereospecific 1,2-cis glycosylation of 2-O-allyl-protected glucosyl and ma nnosyl fluorides via a sequence of allyl isomerization, N-iodosuccinimide-m ediated tethering, and intramolecular aglycon delivery (IAD) is reported, T he use of fluoride as anomeric leaving group is advantageous in that tether ing efficiencies can be increased for hindered aglycon alcohols by the use of extended reaction times without competitive anomeric activation, Intramo lecular glycosylation furnishes the desired alpha -glucosides and beta -man nosides in an entirely stereoselective manner.