652
3
Chemical Glycosylation Reactions
⊡ Scheme 85
3,4-Dimethoxybenzyl 2-deoxy glycosides as glycosyl donors
⊡ Scheme 86
Bromobutyl glycosides as glycosyl donors
acid promoter (AgOTg) to give disaccharides 506 and 509 in moderate yields. The suggested
reaction pathway involved a spontaneous, or acid, triggered, 5-exo-tet cyclization of the bromobutyl glycoside, e. g. 508→510, to form an anomeric furanosyl cation 510, which would
evolve to give non-nucleophilic volatile tetrahydrofuran, and oxocarbenium ion 511. The latter
will then react with acceptor 40 to furnish the disaccharide.
Hung and co-workers have reported on the use of 2-allyloxyphenyl mannoside 512 as a useful
glycosyl donor [245]. Mannoside 512 reacted in the presence of NIS/TfOH in CH 2 Cl 2 at room
3
Chemical Glycosylation Reactions
⊡ Scheme 85
3,4-Dimethoxybenzyl 2-deoxy glycosides as glycosyl donors
⊡ Scheme 86
Bromobutyl glycosides as glycosyl donors
acid promoter (AgOTg) to give disaccharides 506 and 509 in moderate yields. The suggested
reaction pathway involved a spontaneous, or acid, triggered, 5-exo-tet cyclization of the bromobutyl glycoside, e. g. 508→510, to form an anomeric furanosyl cation 510, which would
evolve to give non-nucleophilic volatile tetrahydrofuran, and oxocarbenium ion 511. The latter
will then react with acceptor 40 to furnish the disaccharide.
Hung and co-workers have reported on the use of 2-allyloxyphenyl mannoside 512 as a useful
glycosyl donor [245]. Mannoside 512 reacted in the presence of NIS/TfOH in CH 2 Cl 2 at room