Microbial oxygenation of cycloheptyl-N-phenylcarbamate and (+/-)-trans-2-fluorocycloheptyl-N-phenylcarbamate with Beauveria bassiana

The title biotransformation of 1 gave trans-4-hydroxycyclohept-1-yl-carbamate (3, 10%, 62% eel, its consecutive ketone 5 (12%) and the racemic cis-isomer 4 (1.8%). Similarly, the racemic trans-2-fluoro analogue 2 yielded mainly four optically active alcohols 7 (24%,, 82% ee), 8 (8%, 16% ee), 9 (4.5%, 52% ee) and 10 (5%, 79% ee) by partial kinetic resolution. The fluorine substituent near the anchoring electron rich group caused a remarkable drop in regio-and diastereoselectivity, but increased the enantioselectivity. Obviously, there is not simply an isosteric substitution of a hydrogen in this position, but the electronic effect by fluorine strongly influences the binding mode. Probably 1 and the two enantiomers of 2 can be attached in different geometry to the active site of the enzyme. (C) 1997 Elsevier Science Ltd.