Development of chiral stationary phases consisting of low-molecular-weight cellulose covalently bonded to silica gel

我们制备了手性载体，其手性固定相（CSP）由低分子量纤维素衍生物（聚合度：15）组成，与硅胶共价键合。作为CSP基料的纤维素在偶联反应前用磷酸预水解，使纤维素中的还原末端与硅化二氧化硅表面的氨丙基结合。用3,5-二氯苯异氰酸酯或苯基异氰酸酯取代纤维素中的羟基后，我们测试了由此获得的CSP的手性识别性能，发现其具有广泛的手性识别能力。我们还证实，使用“强”溶剂作为流动相可以实现洗脱，这对于涂层型CSP来说是困难的，因为流动相可能会溶解CSP。然而，更多的对映体混合物在涂层型csp上比在共价键合的csp上有更大的选择性因子（α）。由低分子量苯氨基甲酸纤维素组成的包覆型CSP作为对照样品，其性能与市售包覆型CSP柱(CHIRALCEL【〇！R】OC)，因此化学键合的CSPs性能稍差的原因可能是由于CSPs固定在硅胶上，因此组成CSPs的聚合物难以获得手性识别所需的最佳超分子结构。低聚合度可能会产生额外的影响。

We prepared chiral supports whose chiral stationary phase (CSP), consisting of a low-molecular-weight cellulose derivative (degree of polymerization : 15), is covalently bonded to silica gel. The cellulose used as the base material of the CSP was pre-hydrolysed with phosphoric acid before the coupling reaction to unite a reducing terminal in the cellulose and anaminopropyl group on the surface of silanized silica. After substituting hydroxyl groups in cellulose by using 3,5-dichlorophenyl isocyanate or phenylisocyanate, we tested the CSP thus obtained for its performance in chiral recognition and found a wide range of chiral discrimination ability. We also confirmed that an elution using ‘strong' solvents as a mobile phase could be achieved, which is difficult for the coated-type CSPs because the mobile phase may dissolve the CSP. However, more enantiomeric mixtures showed larger selectivity factors (α) when eluted on the coated-type CSPs than on the covalently bonded CSPs. A coated-type CSP consisting of the low-molecular-weight cellulose phenylcarbamate, prepared as a control CSP sample, showed comparable performance with the commercial coated-type column (CHIRALCEL【○!R】 OC), so the slightly poorer performance of the chemically bonded CSPs may be explained by the difficulty of the polymer consisting of the CSPs in taking an optimal supermolecular structure required for chiral recognition due to the fixation to the silica gel. The low degree of polymerization may have an additional effect.