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N
3
O
N
N
BnO
O
BnO
OH
N
BnO
N
HO
N
N
N
O
HO
OH
HO
(i) CuI, DIPEA,
toluene, rt, 24h
N
N
HO
OH
O
BnO
BnO
N
(ii) Pd/C, NH
4
HCO
2
,
50°C, 16h
OH
OH
HO
BnO
O
OH
N
N
N
N
N
HO
N
N
O
N
O
BnO
BnO
151
BnO
N
N
N
O
BnO
BnO
BnO
150
SCHEME 5.32
Synthesis of C-cyclodextrin-like analogs.
mode, clustering of receptors or statistical rebinding [52]. Hundreds of synthetic
multivalent glycomimetics with diverse geometries, numbers of epitopes, and degrees
of freedom have been synthesized. Such glycoconjugates have been classified as
glycodendrimers, glycoclusters, glycopolymers and glycoproteins depending on the
nature of their scaffold [40].
Compared to dendrimers or polymers, there are few reports on the use of car-
bohydrates as scaffolds in the synthesis of multivalent ligands [8, 53]. Some of
the examples correspond to glycosylamide scaffolds and cyclomaltooligosaccha-
ride (cyclodextrin)-centered glycoclusters, the latter already discussed in Section 5.3
[54, 55]. The use of unprotected non-reducing mono or disaccharides as templates
to graft sugar epitopes in all available hydroxyl groups has also been explored [56].
For
in vivo
applications, however, multivalent ligands based on partially deprotected
carbohydrate scaffolds, may result in interesting biological advantages. Improved
hydrophilicity and pharmacokinetics may be expected, for instance, as compared
with peptidic, aromatic, or polymeric scaffolds [57].
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