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Lactose
α
-Cyclodextrin
1) TsCl, Pyridine
2) NaN
3
, DMF, 140 °C
1) Neat propargylamine
2) Ac
2
O, MeOH
(OH)
5
R
OH
OH
OH
O
HO
Ac
93
R=OTs
94
R=N
3
O
HO
O
OH
OH
92
(HO)
12
1) CuSO
4
/Na ascorbate
H
2
O/
i
PrOH
OH
OH
OH
O
HO
Ac
O
HO
O
N
N
(OH)
5
OH
OH
N
95
(HO)
12
SCHEME 5.22
Synthesis of clicked lactosyl cyclodextrins.
Click-assembled glycorotaxanes have been synthesized from building blocks
95
,
96
and
97
as supramolecular systems based on host-guest inclusion complexes, con-
stituted by a glycosylated-
-cyclodextrin conjugate and a decane guest (Scheme 5.22
and Scheme 5.23). Oligorotaxanes carrying up to five cyclodextrin units were isolated
(67% yield for compound
100
) and characterized by MS and NMR experiments (1D
five and diffusion-ordered spectroscopy [DOSY]). Their abilities to inhibit the bind-
ing of
Arachis hypogaea
agglutinin to asialofetuin was evaluated by enzyme-linked
lectin assays (ELLA) [42].
5.4 TRIAZOLE-LINKED MACROCYCLES
An interesting application of the 1,3-dipolar cycloaddition is the synthesis of macro-
cycles, as mimetics of cyclodextrins and other cyclic oligomers capable to host
different molecules. Earlier examples of cyclodextrin analogs obtained by thermal
cycloaddition have been reported by Vasella and coworkers [43]. The desired
intramolecular 1,3-dipolar cycloaddition took place at 110
◦
C and gave the 1,4- and
1,5-substituted 1,2,3-triazoles
106
(24%) and
108
(31%), which were separated by
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