Towards a tandem-radical macrocyclization-transannular cyclization approach to steroids: Transannular cyclizations of a macrocyclic core

Article abstract of DOI:10.1016/0040-4039(95)01918-8

The triple transannular radical cyclization of 1-cyano-5-methyl-1-phenylseleno-8-hydroxy-4,9,13-cycloheptadecatriene (1a) provided a product 2 possessing the steroid ring skeleton of unassigned configuration in 4% isolated yield. A high yielding transannular cyclization of the related diene lacking the Δ^4,5-double bond identifies the second cyclization as the Achilles heel of the triene cyclization.