O-Glycosyl Donors
3.4
627
⊡ Scheme 58
Oxathiines: vinyl glycoside donors for the synthesis of 2-deoxy glycosides
⊡ Scheme 59
Stereocontrol in the formation of 2-deoxy glycosides from oxathiines
were prepared by reaction of carbohydrate hemiacetals with the corresponding activated fluoroarenes in the presence of a base. The use of 4-(N,N-dimethylamino)pyridine (DMAP) gave
an α/β ratio similar to the starting 1-OH, i. e. predominantly α. In contrast, the formation of
β-DISAL donors was favored using 1,4-dimethylpiperazine as base. The fluoroarenes were
prepared by nitration of 2-fluoro- or 4-fluoro-benzoic acid.
The preparation of disaccharides, from benzyl-protected DISAL donors (e. g. 367, > Scheme
61), was best carried out in 1-methylpyrrolidin-2-one (NMP), a high polar, aprotic solvent,
3.4
627
⊡ Scheme 58
Oxathiines: vinyl glycoside donors for the synthesis of 2-deoxy glycosides
⊡ Scheme 59
Stereocontrol in the formation of 2-deoxy glycosides from oxathiines
were prepared by reaction of carbohydrate hemiacetals with the corresponding activated fluoroarenes in the presence of a base. The use of 4-(N,N-dimethylamino)pyridine (DMAP) gave
an α/β ratio similar to the starting 1-OH, i. e. predominantly α. In contrast, the formation of
β-DISAL donors was favored using 1,4-dimethylpiperazine as base. The fluoroarenes were
prepared by nitration of 2-fluoro- or 4-fluoro-benzoic acid.
The preparation of disaccharides, from benzyl-protected DISAL donors (e. g. 367, > Scheme
61), was best carried out in 1-methylpyrrolidin-2-one (NMP), a high polar, aprotic solvent,