From Homer to hedgehog: Cyclopamine, the first inhibitor of the hedgehog signaling pathway, causes cyclopia in embryos but in adults it is a potent anticancer drug. A concise biomimetic and diastereoselectivesynthesis of cyclopamine (2) starting from commercially available dehydroepiandrosterone (1) now also provides access to several analogues.
A biomimetic three-step transformation of classical "6-6-6-5"-steroids into their C-nor-D-homo-counterparts gives an easy and fast access to this highly important substructure of natural products, as it is found in cyclopamine, and nakiterpiosin. A novel reagent combination allows for the rearrangement even of 17-keto steroids with high endoselectivity. In several examples the broadness of this strategy