The present invention relates to optically pure bis(o-diarylphosphinophenyl)-tetrahydro-bi(1,3-oxazole) compounds represented by the formula (I) and a preparation method thereof.  Bis(o-diarylphosphinophenyl)-tetrahydro-bi(1,3-oxazole) compounds of the present invention include (4S,4'S)-2,2'-bis(o-diarylphosphinophenyl)-4,4',5,5'-tetrahydro-4,4'-bi(1, 3-oxazole) as represented by the formula (Ia) and its optical isomer, (4R,4'R)-2,2'-bis(o-diarylphosphinophenyl)-4,4',5,5'-tetrahydro-4,4'-bi(1, 3-oxazole) as represented by the formula (Ib) depending on the absolute ratio of the initial reactant, tartaric acid. 
Generally, optically pure compounds are increasingly demanded recently since the optical isomers have different biological properties.  Therefore, preparation methods for the optically pure compounds are required greatly.  Especially, the asymmetric hydrosilylation, hydrogenation, cyclopropylation, alkylation using the metallic catalysts such as Rh, Ru, Ir, Co, Cu and Pd are used in preparing the optically pure compounds.  Therefore, development of an effective ligand for these reactions is absolutely necessary in developing the medicines, pesticides, food additives and fragrances.  To date, the most widely developed chiral ligands for the asymmetric catalytic reaction are phosphine and oxazoline compounds that contain phosphorus and nitrogen, respectively.  Some of the chiral compounds of the previous art, however, have a room for improvement.  For instance, the bisphosphine chiral ligand for the hydrosilylation of ketones by using the metallic Rh(l) such as 2,3-o-isopropyliden-2,3-dihydroxy-1,4-bis(diphenylphosphinobutane (DIOP) was used to obtain the product with only 60% of optical purity (Organometallics, 1991, 10, 500).  Another study shows that the product with an average of more than 90% optical purity was obtained by using an optically pure bis(oxazolyl)pyridine ligand with, however, a shortcoming that more than 4 to 10 equivalent weights of the excess ligand had to be used for the reaction (Organometallics, 1989, 8, 846; J. Organomet.  Chem.  1988, 346, 413).