Development of new supported asymmetric catalysts based on biopolymers

本研究以壳聚糖等生物大分子的区域选择性转化为目标，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poly[ß-(1-&gt；4)-2-amino-2-deoxy-D-glucopyranose]是由甲壳素N-脱乙酰基得到的多氨基糖，甲壳素是仅次于纤维素的第二丰富的生物聚合物。甲壳素是从甲壳类外骨骼中提取的，是一种未被开发的资源，盛产于加拿大沿海地区。每个单元的壳聚糖将被区域选择性地转化为螯合性氨基膦或亚磷酸配体，以获得多配体。有机可溶性多配体是通过在O-6位引入有机基团来合成的。另一方面，通过在伯醇上引入极性基团和离子基团，形成了水溶性的多配体。这些多配体的配位将通过具有不同金属中心的光谱来研究。近年来，天然产物衍生物作为不对称催化剂得到了广泛的研究。然而，用于催化的手性载体实例很少。壳聚糖固有的手性将被用来在催化反应中诱导不对称性。负载型不对称催化剂将用于C=C-O(环状)、C=C-CH2OH和C=C-Coor的模型化合物的加氢反应。由于壳聚糖的聚合性，负载型催化剂可以通过沉淀法或过滤法进行回收。不对称催化是制备对映体纯化合物最有效的方法，因此，它对化学工业，尤其是制药、食品和新材料工业具有重要的经济意义。该研究项目还通过开发用于水介质中不对称催化、生物质价态和生物可降解聚合物转化的可溶性不对称载体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.