Habrant , D & Koskinen , A M P 2010 , ' Towards the total synthesis of calyculin C: Preparation of the C9-C25 spiroketal-dipropionate unit ' ORGANIC AND BIOMOLECULAR CHEMISTRY , vol 8 , no. 19 , pp. 4364-4373 . DOI: 10.1039/c0ob00092b
Abstract:
An asymmetric synthesis of the C9 –C25 spiroketal fragment of calyculin C is described. Key steps include two crotylation reactions using successively Brown’s reagent and (Z)-crotyltrifluorosilane for the formation of the anti, anti, anti stereotetrad, ynone formation by a Pd-catalyzed coupling of a thiol ester with a terminal alkyne and a double intramolecular hetero-Michael addition for the stereoselective construction of the spiroketal framework.