Development of new supported asymmetric catalysts based on biopolymers

该研究计划的目标是区域选择性转化生物聚合物如壳聚糖，合成负载型不对称催化剂，以实现有机，水和两相介质中的催化反应。壳聚糖或聚[β-（1->4）-2-氨基-2-脱氧-D-吡喃葡萄糖]是从几丁质N-脱乙酰化获得的聚氨基糖，其是继纤维素之后第二丰富的生物聚合物。甲壳素是从甲壳类动物的外骨骼中提取的，是加拿大沿海地区丰富的一种未充分开发的资源。壳聚糖的每个单元将区域选择性地转化为螯合的氨基亚磷酸酯或亚磷酸酯配体，以获得多配体。通过在O-6位引入有机基团，合成了可溶性有机多配体。另一方面，通过在伯醇上引入极性和离子基团形成水溶性多配体。这些多配体的配位将通过光谱与不同的金属中心进行研究。近年来，天然产物衍生物作为不对称催化剂被广泛研究。然而，用于催化的手性载体实例是罕见的。壳聚糖的固有手性将被用来诱导催化反应过程中的不对称性。负载型不对称催化剂将用于具有C=C-O（环状）、C= C-CH_2 OH和C=C-COOR功能的模型化合物的加氢。由于壳聚糖的聚合性质，负载型催化剂可以通过沉淀或过滤方法回收。不对称催化是制备对映体纯化合物的最有效方法，因此，它对化学工业，特别是对制药，食品和新材料工业具有重要的经济意义。该研究计划还通过开发用于水介质中不对称催化的可溶性不对称载体，生物质价值评估和生物可降解聚合物转化来满足一些环境目标。

This research program has for objectives the regioselective transformation of biopolymers like chitosan to synthesize supported asymmetric catalysts to realize catalytic reactions in organic, aqueous and biphasic media. Chitosan or poly[ß-(1->4)-2-amino-2-deoxy-D-glucopyranose] is polyaminosaccharide obtained from chitin N-deacetylation which is the second more abundant biopolymer after cellulose. Chitin is extracted from crustacean exoskeletons and represents an underexploited resource that abounds in coastal regions of Canada. Each unit of chitosan will be regioselectively transformed in a chelating aminophosphinite or phosphite ligands to obtain a polyligand. Organic soluble polyligands are synthesized by introduction of organic groups at O-6 positions. On the other hand, water soluble polyligands are formed by introduction of polar and ionic groups on primary alcohols. Coordination of these polyligands will be studied by spectroscopy with different metallic centers. Recently, natural products derivatives were studied as asymmetric catalysts. However, chiral support examples used in catalysis are rare. Intrinsic chirality of chitosan will be utilized to induced asymmetry during catalytic reactions. Supported asymmetric catalyst will be used for hydrogenation of model compounds with function as C=C-O (cyclic), C=C-CH2OH and C=C-COOR. Due to the polymeric nature of chitosan, supported catalysts could be recuperated by precipitation or filtration methods. Asymmetric catalysis is the most efficient method to prepare enantiomerically pure compounds and therefore, it represents a major economic importance for chemical industries, and more specifically for pharmaceutical, foods and new material industries. This research program also meets some environmental objectives by the development of soluble asymmetric supports for asymmetric catalysis in aqueous media, biomass valorization and biodegradable polymers transformation.