Preparation of saccharide-silica composites by a sol-gel method and the application for optical resolution of metal chelate compounds

A novel organic-inorganic composite was prepared by a sol-gel process using hydrolysis and condensation of tetraethoxysilane (TEOS) reacted with a sac charide. During the process, ethoxy groups of the TEOS were replaced with h ydroxyl groups of the saccharide and, consequently, saccharide molecules we re combined with silica through their hydroxyl groups. Samples obtained und er different reaction conditions were used for optical resolution of a meta l chelate compound. The resolution ability of the composites was affected b y the amount of water added for hydrolysis and of the saccharide. In partic ular, the amount of water drastically influenced the optical resolution per formance. Composites obtained at the lower H2O/TEOS ratio gave the metal ch elate compound a higher optical rotation. Three types of composites with th e same composition were prepared by kneading, impregnation and by the sol-g el method, and were compared. The sol-gel composite showed the best optical resolution ability. It was concluded that the optical resolution ability w as closely related to dispersibility of saccharide in the silica matrix.