The anomalous course of the microsomal transformation of the exo-2,3-epoxides of norbornene and norbornadiene. The possible involvement of a general acid activation during the enzymatic hydrolysis of these oxides

The enzymatic hydrolysis of exo-2,3-epoxy-norbornane (1) with a crude rabbit liver microsomal preparation occurred with a rearrangement and gave selectively (2R,7S)-bicyclo[2.2.1]heptane-2,7-diol (3), enantiomeric excess (ee) 30±2%. The analogous exo-2,3-epoxy-5-norbornene (2) gave, under the same conditions, exclusively endo-6-hydroxymethylbicyclo[3.1.0]hex-2-ene (4), arising from the microsomal catalyzed reduction of the first formed endo-6-formylbicyclo[3.1.0]hex-2-ene (5). A mechanistic explanation for the observed products is proposed.