Chitosan Derivatives - Chitosan Based Hydrogels: Functions and Applications - page 71

was linked to chitosan by reductive amination. 2- O -formylmethyl-α-CD was prepared by
selective allylation of α-CD and subsequent ozonolysis of the C-C double bond in the
resulting mono-allylated derivative [224]. The reaction scheme and conditions are given in
Figure 2.28. All the derivatives obtained were found to be soluble in water and in alkaline
solvents such as aqueous ammonia and aqueous sodium hydroxide, except for that with a
DS of 11%, which was soluble only in acidic solution.

2.10.6 grafting of CD onto Chitosan via epoxy-Activated Chitosan

Recently, a new synthetic route was reported to graft β-CD onto chitosan using epoxy-
activated chitosan as shown in Figure 2.29 [225]. The adsorption properties of this product
for p -dihydroxybenzene were studied and compared with that of chitosan and β-CD-graft-
6-chitosan that was synthesized by the reaction of mono [6- O -( p -toluenesulfonyl)]-6-β-CD
with chitosan. The grafting of β-CD onto chitosan resulted in higher adsorption capacities
for p -dihydroxybenzene than for chitosan.

2.10.7 grafting of CD onto Chitosan by using a redox initiator

β-CD-graft-chitosan was prepared by reacting β-CD itaconate vinyl monomer with chito-
san using ceric ammonium nitrate (CAN) [226]. In this work, β-CD itaconate was prepared

H

O

OH

HO O O

HO HO OH

O

a

b c

CD

OH

N

Mono 2-O-allyl-CD

2-O-(formylmethyl)-CD

OH

O

HO

O

OH

d

NH

O

HO

Figure 2.28
Reaction scheme and conditions for the synthesis of α-CD-graft-chitosan: (a) LiH-LiI, DMSO, and then allyl
bromide, 60°C, overnight; (b) O 3 in 50% aqueous MeOH, 0°C, 4 h, and then Me 2 S, 25°C, overnight; (c) chitosan in
acetate buffer (pH 4.4), 25°C, 1 h; and (d) NaBH 3 CN in acetate buffer (pH 4.4), 25°C, 4 days. (From Tojima, T. et al.
1998. J Polym Sci A-Polym Chem 36: 1965-1968. With permission.)