Marker degradation

Although a natural corticosteroid, cortexolone may be obtained in large amounts by chemical transformation from 16-dehydropregnenolone acetate, an intermediate in the Marker degradation of diosgenin (Figure 5.119). 

The electrochemical oxidation of metal ions (e.g., Ag+ - Ag2+) for the catalytic oxidation of organic compounds has been practiced on a small scale.24 The feasibility of recycling Cr3+ produced from Cr6+ in the Marker degradation of diosgenin acetate is outlined in Chapter 11. 

Later the estrone produced for commercial purposes was obtained from diosgenin. Diosgenin was first oxidized to its l,4,6-triene-3-one derivative, which was aromatized by pyrolysis at 500-600°C,50 subjected to the Marker degradation and the 17-acetyl group removed by Beckmann rearrangement of the 20-oxime. The overall Syntex process51 for the manufacture of Norethindrone from diosgenin (XVIII) is outlined in Scheme 5. 

An attractive route was based on hecogenin (55), freely available from the East African sisal plant, (ref.50) by conversion to the dibromide which was transformed to the 12-hydroxy-11-one and thence as the diacetate by reduction to the ll-keto compound shown in an overall yield of 55% from hecogenin. Side-chain Marker degradation afforded cortisone (ref.51) after further steps. 

Marker, R. E. Tsukamoto, T. Turner, D. L. J. Am. Chem. Soc. 1940, 62, 2525-2532 American Chemical Society International Historic Chemical Landmarks. The Marker Degradation and Creation of the Mexican Steroid Hormone Industry 1938-1945. http //www.acs.org/content/acs/en/education/ whatischemistry/landmarks/progesteronesynthesis.html (accessed February 16, 2015). 

---