624
3
Chemical Glycosylation Reactions
of the acetyl groups will give an assortment of acceptors. The pool of compounds can be split,
and in combinatorial steps each pool of glycosyl acceptors can be coupled with a particular
glycosyl donor (D 1→4 ) resulting in four libraries of 32 (or 64, as above) trisaccharides each.
Branched Trisaccharide Libraries Biologically important oligosaccharides often contain
more complex features such as branching points and further functional groups. In this context,
Boons and co-workers, using the latent-active strategy, designed a synthetic method to create
orthogonally protected saccharides (acetyl and p-methoxybenzyl groups were used as orthogonal protecting groups) that could be easily further derivatized [181]. Thus, a common allyl
glycoside building block (e. g. 335, > Scheme 55) can be converted to two vinyl glycoside
donors bearing orthogonal protecting groups (e. g. 336 and 338), and to an allyl glycosyl
acceptor 337, bearing one free hydroxyl and one selectively removable PMB ether. The latter
will be coupled with donor 336 bearing an acetyl protecting group to give an orthogonally
⊡ Scheme 56
3-Buten-2-yl derivatives for the synthesis of amino sugar containing disaccharides
3
Chemical Glycosylation Reactions
of the acetyl groups will give an assortment of acceptors. The pool of compounds can be split,
and in combinatorial steps each pool of glycosyl acceptors can be coupled with a particular
glycosyl donor (D 1→4 ) resulting in four libraries of 32 (or 64, as above) trisaccharides each.
Branched Trisaccharide Libraries Biologically important oligosaccharides often contain
more complex features such as branching points and further functional groups. In this context,
Boons and co-workers, using the latent-active strategy, designed a synthetic method to create
orthogonally protected saccharides (acetyl and p-methoxybenzyl groups were used as orthogonal protecting groups) that could be easily further derivatized [181]. Thus, a common allyl
glycoside building block (e. g. 335, > Scheme 55) can be converted to two vinyl glycoside
donors bearing orthogonal protecting groups (e. g. 336 and 338), and to an allyl glycosyl
acceptor 337, bearing one free hydroxyl and one selectively removable PMB ether. The latter
will be coupled with donor 336 bearing an acetyl protecting group to give an orthogonally
⊡ Scheme 56
3-Buten-2-yl derivatives for the synthesis of amino sugar containing disaccharides