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NH
2
Br
O
N
N
N
N
N
N
HO
HO
R
O
O
OH
OBz
OBz
1a
1b
FIGURE 12.1
Sugar-based triazoles known before invention of CuAAC reaction.
unnatural glycosidic linkages. An appreciable benefit of the latter approach is that
the “artificial” glycoconjugate may retain the geometric and spatial characteristics
of the native glycoform with sufficient hydrolytic stability toward glycosidases and
glycosyltrasferases and also inhibit these enzymes to some extent, so increasing the
potential for a wide array of
in vivo
applications [30]. In medicinal chemistry, the 1,4-
disubstituted 1-
H
-1,2,3-triazoles have been considered significant for diverse range
of
in vivo
applications, and indeed before the discovery of CuAAC reaction, more
than 7000 1,4-disubstituted triazoles have been known (Fig. 12.1).
More recently, Cu(I)-catalyzed click reaction has emerged as powerful conjugation
strategy for the discovery and optimization of structurally diverse glycoconjugates of
biomedical interest [29].
N
N
NN
N
3
N
N
RuAAC
CuAAC
+
1,4-Triazole
1,5-Triazole
1
2
Huisgen DCA
Heating
N
N
N
N
N
N
1,4-Triazole
1
1,5-Triazole
2
SCHEME 12.1
Regioselectivity in alkyne-azide 1,3-dipolar cycloaddition reaction.
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