Biomedical Engineering Reference
In-Depth Information
5.7
Chemoenzymatic Synthesis of Amylose-
Grated Silica Gel
The chiral recognition ability of amylose derivatives is one of the
significant functions for their practical use of the amylose-conjugated
materials [39]. On the basis of this viewpoint, silica gel bounded
by amylose through the phosphorylase-catalyzed enzymatic
polymerization was prepared, and the chiral recognition ability of
its phenylcarbamate derivative was investigated [40].
Two kinds of synthetic approaches are illustrated in Figs. 5.8
and 5.9. In approach (I), Glc
lactone was first prepared, followed
by reaction with 3-aminopropyltriethoxysilane to obtain the
maltooligosaccharide bearing triethoxysilyl group. Amylose chains
were then extended by the phosphorylase-catalyzed enzymatic
polymerization, and the resulting amylose derivative was allowed to
react with silica gel to produce amylose-grafted silica gel (Fig. 5.8). In
approach (II), Glc
5
was first oxidized to be converted into a potassium
gluconate at a reducing terminal residue, and the enzymatic
polymerization was then performed. After the lactonization, the
amylose was immobilized onto the silica gel to obtain amylose-
grafted one (Fig. 5.9). Finally, both the amylose-grafted silica gels
were treated with a large excess of 3,5-dimethylphenyl isocyanate
to derivatize the remaining hydroxy groups of amylose to the
carbamates (Figs. 5.8 and 5.9).
5
OH
OH
O
O
HO
HO
HO
HO
OH
OH
OH
O
OH
O
HN
Si(OEt)
3
OH
O
O
HO
HO
HO
O
OH
O
OH
O
O
HO
OH
OH
O
3
3
OH
+
OH
H
2
N
Si(OEt)
3
Glc-1-P
Phosphorylase
OH
OH
Silica gel
O
O
HO
HO
HO
HO
HO
OH
OH
O
OH
O
OH
O
HN
Si
Silica gel
HN
Si(OEt)
3
O
O
HO
HO
HO
HO
O
OH
O
OH
O
O
OH
OH
OH
OH
n
n
OH
OH
OCN
OR
O
RO
RO
OR
O
OR
O
Silica gel
HN
Si
O
RO
RO
O
OR
O
OR
OR
n
O
N
R =
C
OR
Figure 5.8
Synthetic approach (I) for amylose-grafted silica gel.
