Towards a tandem-radical macrocyclization-transannular cyclization approach to steroids: Transannular cyclizations of a macrocyclic core
作者:Ullrich Jahn、Dennis P. Curran
DOI:10.1016/0040-4039(95)01918-8
日期:1995.12
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 Δ4,5double bond identifies the second cyclization as the Achilles heel of the triene cyclization.
1-氰基-5-甲基-1-苯基硒基-8-羟基-4,9,13-环庚二烯(1a)的三环环戊基自由基环化提供了具有未分配构型的类固醇环骨架的产物2,分离产率为4%。缺少Δ相关二烯的高产跨环环化4,5-双键标识第二环化作为三烯环化的致命弱点。