Chemistry Reference
In-Depth Information
This methodology was applied in a one-pot approach from unprotected or acetylated
monosaccharides reported by Wang (Scheme 5.3) [25]. Acetylation of D-ribose with
acetic anhydride in the presence of a trace amount of iodine as catalyst was followed
by brominolysis of the anomeric acetate. After removal of all volatiles and further
conversion to the anomeric azide, an
in situ
CuAAC-promoted reaction afforded the
triazolylglycoside
10
in 74% yield.
The functionalization of C-3 and C-5 of a sugar central unit with alkyne
groups followed by the reaction of 1-azido mannofuranoside in the presence of a
Cu(I) catalyst, generated 1,2,3-triazole-linked trisaccharide carbohybrid analog
11
(Scheme 5.4) [26].
Triazol-linked disaccharide analogs as
13
have also been prepared using water as
solvent, by reaction of 1-azido-1-deoxy-2,3,4,6-tetra-
O
-acetyl-
-D-glucopyranose
with the corresponding terminal alkynes in the presence of CuSO
4
/ascorbic acid
(Scheme 5.5) [27].
Wilkinson and coworkers studied the relative rate of cycloaddition by using a
variety of alcohol co-solvents and reaction temperatures. It was found that the reaction
proceeded with similar efficiency irrespective of the co-solvent used; however, mildly
elevated temperatures (40
◦
C) increased the speed of reaction significantly. They
verified that, when using anomeric azides, the anomeric configuration is preserved
during the reaction [28].
In our laboratory, we have developed a procedure to connect saccharide residues
by click chemistry. This approach showed that different sugars bearing an azide on
C-2, C-5 or C-6 (compounds
14-17
) can be used as building blocks in the syn-
thesis of complex oligosaccharidic mimetics by reacting with alkynyl glycosides
18
-
21
(Scheme 5.6) [29]. The reaction tolerates the wide range of protecting groups
O
O
O
O
N
N
N
O
O
O
O
O
O
O
O
O
N
N
N
O
O
11
SCHEME 5.4
Trisaccharide carbohybrid analog.
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