Dehydrative glycosidation reactions reported by the authors' group are reviewed. The authors' efforts were concentrated on developing
reagent systems usable for one-stage-one-pot glycosidation. Such systems could simplify the glycosidation step using 1-OH
sugar derivatives, since any preactivation stage for the hemiacetal
OH group could be omitted. The systems, utilizing the
dehydration potential of
sulfonyl chloride, such as the
p-nitrobenzenesulfonyl chloride-
silver trifluoromethanesulfonate-
triethylamine system as well as the
p-nitrobenzenesulfonyl chloride-
silver trifluoromethanesulfonate-
N,N-dimethylacetamide-
triethylamine system, were useful for the syntheses of many kinds of
oligosaccharides. As a system free from any metals, the authors developed the
trimethylsilyl trifluoromethanesulfonate-
pyridine (TP) system. During the study of the system containing
cobalt (II)
bromide, the authors found that the
bromide converts 1-OH
sugar into the corresponding 1-Br derivative, which is then activated with the
cobalt salt to undergo glycosidation with alcohol. To prepare partially benzylated
sugar derivatives used as acceptors in the authors' studies, controlled benzylation and forced tritylation were carried out. Short syntheses of a variety of useful
sugar derivatives using such convenient procedures are described. As a novel protecting group for the hemiacetal
OH group, the authors used the 2-methoxyethyl group. Many kinds of
trehalose-type disaccarides we prepared.