PROTON ACID-CATALYZED TRANSFORMATIONS OF ESTROGEN DERIVATIVES - NEW RESULTS AND SOME MECHANISTIC ASPECTS OF THE KOBER COLOR-REACTION

The 3-O-methylated estrogen derivatives 1a-d and alpha-estradiol (1e) underwent sulfuric acid-catalysed transformations to furnish the stero ids 2-6. The processes involved in the reaction sequence are regiosele ctive sulfonation and, above all, the Wagner-Meerwein rearrangement of the methyl group at C-13. With the objective of obtaining further inf ormation on the course of the Kober colour reaction of estrogens, some UV/VIS and ESR spectroscopic investigations were also carried out.