Enantio and diastereoselectivity of cyclohexanone monooxygenase catalyzed oxidation of 1,3-dithioacetals

The asymmetric oxidation of 2-substituted dithianes, dithiolanes and oxathiolanes catalyzed by cyclohexanone monooxygenase (CMO) has been examined. The introduction of substituents at the C-2 causes a decrease of the e.e. with the exception of 2-benzoyl-1,3-dithiane monosulfoxide (90% e.e). With 2-monosubstituted dithioacetals CMO yields preferentially or exclusively the trans diastereoisomer. The binding of the 1,3-dithioacetals at the active site of the enzyme is not only controlled by the sterical hindrance of the substituents in position 2 but also by the configuration at C-2. The stereoselectivity of CMO has been compared with that reported for microsomal flavin and cytochrome P-450 monooxygenases.