Preparation of high functional cellulose derivatives by active esterification and aminolysis

研究了离去基上带有吸电子取代基的乙酸烷基酯的氨基水解反应。DMF的相对速率为：乙酸乙酯为1，-氯乙酸乙酯为37，-氰乙酸乙酯为87，三氯乙酸乙酯为2700。这些反应遵循塔夫脱方程，并得出归纳效应在这些乙酸烷基酯的活化中起重要作用的结论。以DCC为脱水剂，将羧甲基纤维素与具有吸电子基团的醇进行酯化反应。这些活性酯化的纤维素容易发生氨基水解，但由于在酯化过程中在c_2羧基和c_3羟基之间形成内酯环，收率较低，仅为25%。为了防止这种现象，对甲基纤维素（MC）进行了阻断C_2或c_3羟基的羧甲基化。解决了内酯生成的问题。然而，不幸的是，在透析纯化过程中，相当数量的活性酯基被水解。因此，需要不经纯化使用样品或寻找合适的沉淀剂。采用铈（IV）盐将含有活性酯基的乙烯基单体如n -丙烯氧基琥珀酰亚胺接枝到纤维素上。接枝得到了重量增加和红外光谱的证实。淀粉酶在磷酸缓冲液（pH6.3）中固定在接枝纤维素上，温度为37℃。固定化酶的活性约为原淀粉酶的10%，但即使重复使用10次，酶的活性也几乎没有下降。推测固定化酶的低活性与酶活性部分的反应有关，因为活性酯基密度大。为了制备载体拆分光学异构体，允许具有活性酯基和异氰酸酯基的纤维素与(R) -2-氨基-1-丁醇反应。

The aminolyses of alkyl acetates carrying electron-withdrawing substituents in leaving groups were investigated. The relative rates in DMF were found to be as follows : 1 for ethyl acetate, 37 for beta-chloroethyl acetate, 87 for beta-cyanoethyl acetate, and 2700 for trichloroethyl acetate. These reactions followed the Taft equation, and it was concluded that the inductive effect plays an important role in the activation of these alkyl acetates.Carboxymethyl cellulose was esterificated with alcohols having electron-withdrawing groups, using DCC as the dehydrating sgent. The aminolyses of these actively esterificated celluloses took place easily, but yields were low, e.g.25% because of the formation of lactone ring between C_2-carboxyl and C_3-hydroxyl groups during the esterification.To prevent this phenomenum, carboxymethylation of methyl cellulose (MC) in which C_2 or C_3-hydroxyl groups were blocked was carried out. The problem of lactone formation was solved. Unfortunately, however, considerable amount of active ester groups were hydrolyzed during purification by the dialysis. Thus it is needed that the samples are used without purification or proper precipitating agent is seeked.Vinyl monomers bearing active ester group such as N-acryloxy succinimide were prepared and grafted onto cellulose using cerium (IV) salt. Grafting was confirmed by an increase in weight and IR spectra. Amylase was immobilized onto the grafted celluloses in the phosphoric acid buffer (pH6.3) solution at 37ﾟC.The activity of immobilized enzyme was about 10% of that of original amylase, but the activity was little lowered even after repeated usage 10 times. It was speculated that the low activity of immobilized enzyme depends on the reaction of active parts of enzyme because of high density of active ester groups. To prepare the carrier resolving optical isomers, celluloses with active ester groups and also isocyanate groups were allowed to react with (R) -2-amino-1-butanol.