Development of a new method for choromatographic resolution by use of a clay

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In the present project, we have attempted to develop a new chromatographic method for the quantitative separation of an optical isomer using a clay-chelate adduct as a packing material.Firstly Yamagishi and Matsushita tried to widen the scope of applicability of a modified clay column for optical resolution. For that purpose, several kinds of optically active metal complexes were applied as a clay modifier such as [Ru(bpy)3]2+ (bpy = 2,2'-bipyridyl) and [Co(phen)3]2+ (pahen = 1,10-phenanthroline). As a result, a clay modified with optically active [Ru(bpy)3]2+ proved to resolve a number of organic compounds. Interestingly enough, the column exhibited different selectivity from the column modified with Ru(phen)3 2+. The column modified with Co(phen)3 2+ did not show any significant separation capability towardsan optically active organic compounds. This may be probably because the chelate posseses three negative charges (+3e) so that the surface density of the adsorbed chelate is too lo … More w to recognize the chility of an approaching molecule. In other words, the results suggest that the resolution is achieved under the cooperative interactions among more than two adsorbed chelates.Secondly Ohtsu has atempted to increase the amount of resolved material from the qualitative scale to the quantitative on. He developed a colum with a size of 60mm(i.d.) x 250 mm and succeeded in resolving 1 - 2 g of a compound such as Ru(acac)3 by one separation procedure. [Ru(acac)3] has been attracting a recent attention as a material for non-linear optics.Thirdly Yamagishi and Matsusita resolved amino acids and dipeptide. As a result, the column packed with a clay (synthetic hectorite) modified with optically active [Ru(phen)3]2+ has proved to resolve many kinds of amino acid esters modified with the 2,5-dinitrobenzoyl group. Moreover the column exhibited high resolution efficiency towards alanyl ala-nine ester modified with the same group. The resolution mechanisms were studied with NMR spectroscopy in acetonitrile.Lastly Yamagishi has performed the theoretical investigations on the adsorption of a metal complex by a clay by use of Monte Carlo simulation. As a result, it has been revealed that the silicate sheet of a clay has a dominant role in establishing the chirality recognition by a clay modified with an optically active metal complex. Less