Stereochemistry of C-1,2 Dehydrogenation of 5β-Pregnane-3,11,20-trione by Septomyxa affinis

Abstract [1α-2H]- and [1α,2α-2H2]5β-pregnane-3,11,20-trione were prepared from 1α,2α-dideuteriopregn-4-ene-3,20-dione. The C-1,2 dehydrogenation of 5β-pregnane-3,11,20-trione by Δ1-dehydrogenase from Septomyxa affinis was found to proceed by a stereospecific removal of the diequatorially oriented 1α and 2β hydrogens. A mechanism involving loss of the 2β proton by enolization followed by loss of the 1α proton and electron transfer to the C-1,2 position has been proposed.