Chemistry Reference
In-Depth Information
OH
HO
OH
HO
HO
N
N
N
HO
N
N
O
O
N
O
N
N
N
O
O
O
HO
HO
O
+
CuSO
4,
Cu turnings, DMF
MW, 100°C, 15min
HO
O
O
OH
HO
N
3
HO
N
O
HO
O
OH
OH
N
N
HO
HO
N
O
HO
N
N
138
140
139
OH
HO
COO
-
OH
O
O
O
AcHN
Transialidase
HO
135
OMe
Sial
Sial
OH
OH
HO
HO
N
O
O
N
N
N
N
O
O
N
O
N
N
O
N
O
HO
O
+
HO
O
O
OH
N
Sial
O
O
O
OH
N
Sial
N
HO
O
HO
N
N
O
N
142
141
Sial
SCHEME 5.30
Cyclooligomerisation of unprotected 1-azidoalkyne derivatives.
transferred from its CMP-activated form to a propargyl-
-D-galactopyranoside to
give trisaccharide
147
. Further sialylation of
147
resulted in the formation of a
tetrasaccharide
148
. Macrocyclics of different sizes, containing two, three or four
sialic acid residues were synthesized in moderate to excellent yields (30-91%)
after intramolecular dipolar cycloaddition using Cu(I)-DIPEA in 1:1 CH
3
CN-water
(Scheme 5.31).
Recently, Dondoni's group has reported the synthesis of a new family of
cyclodextrin-like macrocycles, containing two, four or six C-glucopyranoside
residues. First, linear oligomers (
150
) have been obtained by sequential clicking of 6-
azido ethinyl residues. Final intramolecular cyclization gave
C
n
-symmetric structures
(74% yield for compound
151)
(Scheme 5.32) [47].
5.5 MULTIVALENT GLYCOCLUSTERS ON
CARBOHYDRATE SCAFFOLDS
Carbohydrate-lectin interactions play a pivotal role in many biological events includ-
ing inflammation [2], immune response, apoptosis, tumor metastasis, or viral and
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