Totalsynthese von (–)‐Norgestrel

Abstract
Total‐Synthesis of (–)‐Norgestrel(–)‐Norgestrel (1a) or (–)‐norethindrone (1b), two active progestational ingredients of currently used contraceptives have been synthesized stereoselectively. Compound 1a has been obtained starting from m‐cresol methyl ether, dimethyl malonate, and (E)‐1,4‐dibromo‐2‐butene. The steroid skeleton has been constructed using an intramolecular DielsAlder reaction of an o‐quinodimethane derivative preceeded by a photo‐enolization of an appropriate methyl‐substituted acetophenone derivative. Chirality has been introduced at an early stage during an ScN reaction (cf. Scheme 1). Compound 1b has been obtained similarly using a previously reported mixture of the enantiomerically pure constitutional isomers 18b/19b (cf. Scheme 3).

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