RESUMEN
Through its collaboration with the ETH in Zurich (Ruzicka's group) and later on with the University of Basel (Reichstein's group). Ciba became involved very early in steroid chemistry. The main task of the chemists consisted at that time of the synthesis of natural hormones and their derivatives. Cholesterol served for several years as the preferred starting material, and efficient procedures were developed for its degradation to suitable intermediates. Total syntheses of estrogenic substances were pursued independently. Up to the mid-1950s the search for alternative starting materials, like hecogenin were intensively investigated. In a later period, collaboration with various companies in the United States and in Europe stimulated Ciba's involvement in the corticoids, especially the dermatocorticoids (Locorten, Sicorten, Miracortene/Ultravate). In line with Ciba's traditionally strong engagement in process development, during the period described in this report a major effort, was directed towards the isolation and synthesis of aldosterone, the most active natural mineralocorticoid. In connection with its partial synthesis, new intramolecular radical reactions (e.g., the lead(IV) acetate and the hypoiodite reaction) were discovered and studied. Although, from the commercial point of view, aldosterone did not meet our expectations, the application of these new reactions to the synthesis of 19-norsteroids opened for Ciba the road to progestins and related compounds.