STEREOSELECTIVITY OF MICROBIAL OXYGENATION OF METALLOCENE SULFIDES WITH DIFFERENT SUBSTITUENT SIZE AND CENTRAL ATOM

Stereoselectivity in the oxidation of ferrocenyl sulphides with severa l species of microorganisms such as Corynebacterium equi was reversed between (methylthiomethyl)ferrocene and (t-butylthiomethyl)ferrocene, indicating that the size of the side chain could control the stereoche mical course of the biooxidation. The size seems to be effective withi n some limit, because the more bulky compound, (phenylthiomethyl)ferro cene, was a poor substrate. On the other hand, the microbial oxidation of (methylthiomethyl)ruthenocene and -osmocene with Mortierella isabe llina and that of (t-butylthiomethyl) ruthenocene and -osmocene with C . equi gave levorotatory sulphoxides (85-97% e.e.): which were all fou nd to have R absolute configuration. These stereoselectivities were th e same as those for the corresponding ferrocenyl sulphides. Thus, the central atom of the metallocenic sulphides seems not to affect the ste reoselectivity in the biooxidation. The microbial oxidation is a usefu l method to prepare several kinds of chiral metallocenic sulphoxides w ith high optical purity.