Application of olefin metathesis in the synthesis of steroids.

Over the past decade, ruthenium-mediated metathesis transformations, including cross-metathesis, ring-closing metathesis, enyne metathesis, ring-opening metathesis polymerization, and also tandem processes, belong to the most intensively studied reactions. Many applications of olefin metathesis in the synthesis of natural products have been recently described. Also in the field of steroid chemistry new methods of total synthesis and hemisynthesis based on metathesis reactions have been elaborated. Various biologically active compounds, e.g. vitamin D and hormone analogues, steroid dimers and macrocycles, etc. have been prepared using a variety of olefin-metathesis protocols.