MICROBIOLOGICAL TRANSFORMATIONS - PART-39 - DETERMINATION OF THE REGIOSELECTIVITY OCCURRING DURING OXIRANE RING-OPENING BY EPOXIDE HYDROLASES - A THEORETICAL-ANALYSIS AND A NEW METHOD FOR ITS DETERMINATION

In the course of this work we have devised new equations as well as a new method allowing for the total determination of the regioselectivit y occurring during biohydrolysis of a racemic epoxide by an epoxide hy drolase. This determination is achievable by simply studying the racem ic epoxide as a substrate. The results showed that, depending on the e nantioselectivity (E value) and the regioselectivity involved, the abs olute configuration as well as the enantiopurity of the residual epoxi de and of the formed diol appear to be highly variable. For a specific enzyme/substrate couple, the yield and enantiopurity of the less reac tive (remaining) epoxide-and thus the possibility to prepare it in ena ntiopure form-exclusively depend upon the enzyme enantioselectivity. O n the other hand, the ee of the formed diol (eep) depends upon the ena ntioselectivity and on the regioselectivity of the oxirane ring openin g. A theoretical analysis based on the material balance, as well as se veral practical examples, are provided to illustrate the various possi bilities of such biohydrolyses. (C) 1998 Elsevier Science Ltd. All rig hts reserved.