Evidence of an enzymatic 17alpha leads to 21 hydroxyl transfer in the biosynthesis of cortexolone from 17alpha-hydroperoxyprogesterone by adrenal cortex microsomes

The concept of a possible biogenetic intramolecular relationship between several pairs of hydroxylated positions of corticosteroids, in particular between positions 17alpha and 21, has been proposed by us some time ago. We now present evidence that to a certain extent such a relationship can indeed exist. 18O-labelled 17alpha-hydroperoxyprogesterone was incubated under ordinary oxygen atmosphere with the microsomal fractions of bovine adrenal cortex. Following extensive purifications by thin-layer chromatography, we have isolated a metabolite with mobility characteristics corresponding to those of authentic 17,21-dihydroxy-4-pregnene-3,20-dione (cortexolone). According to its mass spectrum, this metabolite has a molecular weight of 350, i.e. 4 atomic mass units higher than the molecular weight of non-labelled cortexolone. No conversion of 17alpha-hydroperoxyprogesterone to cortexolone was observed with a previously heat-inactivated preparation. The presence of 4 additional mass units in the cortexolone metabolite means that the latter has preserved two 18O-labels in the molecule, one at position 17alpha and the other one at position 21. This can only be explained by a rearrangement reaction of the hydroperoxide group in such a way that it is accompanied by a C-17alpha to C-21 hydroxyl transfer. In the inverse case, when non-labelled 17alpha-hydroperoxyprogesterone was incubated under 99% 18O2-atmosphere, non-labelled cortexolone of molecular weight 346 was also found.

17 -Hydroperoxypregnenes. IV. A comparative study of the fragmentation by electron impact and high temperature chromatography

The fragmentation of 17α-hydroperoxypregnenolone and 17α-hydroperoxyprogesterone by electron impact and thermolysis is described. It is shown that the fragmentation pattern follows a common pathway for both compounds, determined exclusively by the substituents at ring-D. A new reaction in steroid chemistry, termed deoxygenation, is discovered and its mechanism explained by intramolecular hydrogen abstraction via a six-membered cyclic transition state involving the 20-ketone group.

Biogenetic mechanisms. I. Incorporation of 4-14C-progesterone into gitoxigenin by Digitalis purpurea

In vivo administration of 4-14C-progesterone to a 6-month-old Digitalis purpurea species over a period of 4 weeks resulted in 0.477% incorporation of the radioactivity into gitoxigenin. The identity of the crystalline cardenolide isolated was established by thin-layer and gas chromatography, infrared spectroscopy, as well as isotope dilution with authentic carrier material and crystallization to constant specific activity. The role which progesterone may play as an active precursor in the biogenesis of steroid cardenolides is discussed.