Catalytic asymmetric oxidation of sulfide with titanium–mandelic acid complex: practical synthesis of (S)-3-[1-(2-methylphenyl)imidazol-2-ylsulfinyl]propan-1-ol, the key intermediate of OPC-29030

An effective catalytic asymmetric oxidation of prochiral sulfide 1a to (S)-2a has been achieved by the use of chiral titanium–mandelic acid complex. The enantioselectivity was found to be not influenced by moisture, and moderate to high selectivity (76% ee) was obtained at room temperature (25°C). Thus a practical synthetic method for the platelet adhesion inhibitor, OPC-29030, was established utilising asymmetric oxidation of 1a.