Introduction of 20-Keto Side Chains in 17-Oxosteroids: Wittig-Horner-Emmons Reactions of (E)-17--3-methoxyandrosta-3,5-diene

Article abstract of DOI:10.1021/jo00066a021

The synthesis is described of a series of polyfunctional unsaturated Δ^16,20-20-isocyanosteroids 5a-f by the Wittig-Horner-Emmons reaction of (E)-17<(diethylphosphono)isocyanomethylene> steroid 4 with several aldehydes and with acetone.Hydrolysis of the isocyanosteroids 5a-f with dilute sulfuric acid gave Δ¹⁶-20-ketosteroids 6a-f in high yield.Hydrolysis of 5a was also possible under neutral conditions, via the intermediate Δ^16,20-20-isocyanatosteroid 7a, leading to A-ring protected 16-dehydroprogesterone 8a.The Wittig-Horner-Emmons reaction, together with the described hydrolyses, provides a new method for the introduction of steroid side chains.The method is particularly suited for side chains of different size, structure, and functionality.