Preparation of high functional cellulose derivatives by active esterification and aminolysis

研究了含吸电子取代基的烷基乙酸酯的氨解反应。在DMF中的相对速率为：乙酸乙酯1，乙酸乙酯37，乙酸乙氰乙酯87，乙酸三氯乙酯2700。这些反应遵循Taft方程，认为诱导效应在这些烷基乙酸酯的活化中起着重要作用。以DCC为脱水剂，羧甲基纤维素与含吸电子基团的醇酯化。这些活跃的酯化纤维素很容易发生氨解，但由于酯化过程中C2-羧基和C3-羟基之间形成内酯环，产率较低，例如25%。为了防止这种现象，甲基纤维素(MC)进行了羧甲基化，其中C2或C3-羟基被封闭。解决了内酯的形成问题。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。制备了N-丙烯酰氧基丁二酰亚胺等含活性酯基的乙烯基单体，并用Ce4+盐将其接枝到纤维素上。重量和红外光谱的增加证实了接枝的存在。在37ﾟC的磷酸缓冲液(pH 6.3)中固定化淀粉酶，固定化后的酶活力约为原酶活力的10%，但重复使用10次后酶活力仍略有下降。推测由于活性酯基密度较高，固定化酶的活性较低依赖于酶活性部分的反应。为了制备拆分光学异构体的载体，允许具有活性酯基和异氰酸酯基团的纤维素与(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.