An expedient synthesis of spiroketals: model studies for the calyculin C16–C25 fragment
作者:Vesa Rauhala、Marta Nevalainen、Ari M.P. Koskinen
DOI:10.1016/j.tet.2004.07.059
日期:2004.10
A new short strategy to prepare the spiroketal fragment of calyculins is presented. A novel Seyferth–Gilbert type homologation of hindered lactols to the corresponding alkynes has been achieved for the first time. The spirocyclization was achieved efficiently via a DIHMA (double intramolecular hetero-Michael addition) process of this hindered ynone. The spirocyclization rate is not dependent on the