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New 18‐Substituted Steroids. I. 18‐Methylideneprogesterone
Three independent syntheses of 18‐methylideneprogesterone, the first representative of a new group of biologically highly active steroidal compounds, are described. In the first approach 3‐acetoxy‐20‐oxo‐5‐pregnen‐18‐carbonitril (2) is transformed into the final product by a reaction sequence involving the Cope degradation of the N‐oxide 6 of the corresponding tertiary aminomethyl derivative. The Wittig reaction 3,3,20,20‐Bis(äthylendioxy)‐5‐pregnen‐18‐al (11) represents the crucial step in the second synthesis. In the last procedure the 18‐methylidene‐20‐oxo grouping is generated by fragmentation of an 18,21‐bridged 1,3‐diol system (19). The two former methods are very versatile and generally applicable for the synthesis of other analogues.