Enantiospecific and regioselective opening of 2-alkyl nosylaziridines by indoles mediated by boron trifluoride. Application to a practical synthesis of a GnRH antagonist
作者:Roger N Farr、Ramon J Alabaster、John Y.L Chung、Bridgette Craig、John S Edwards、Andrew W Gibson、Guo-Jie Ho、Guy R Humphrey、Simon A Johnson、E.J.J Grabowski
DOI:10.1016/j.tetasy.2003.08.038
日期:2003.11
An efficient, high yield process for the synthesis of a GnRH antagonist has been developed. We have demonstrated that under boron trifluoride mediation, nosyl aziridines will react with 2-arylindole derivatives to afford β-substituted tryptamines in an enantiospecific process with remarkably high regioselectivity. The scope of the reaction was explored with several 2-substituted nosyl aziridines. The
derivatives that are readily available from both synthetic and biocatalytic approaches undergo gold-catalyzed dearomative cyclizations in aqueousmedia to the corresponding spirocyclic derivatives. In addition to the efficiency of the method, operating in aqueousmedia affords a selective entry to C2-unsubstituted spiroindolenines that have long remained unattainable by Au(I) catalysis. Moderate to excellent