Stereoselective Synthesis of Bicyclo[4.2.1]nonanes - a Temporary-Bridge Approach to Cyclooctanoids

A series of cis-alpha,gamma-difunctionalized five-membered cyclic beta-oxo esters have been chemo-, regio- and diastereoselectively prepared through an efficient domino anionic ring-cleavage/ring-reconstitution/alkylation sequence including a 1,3-shift of the ester group. These unsaturated substrates were successfully engaged in various ring-closing metatheses to provide a reliable access to functionalized bicyclo[4.2.1]nonanes, precursors of cyclooctanoids following the selective fragmentation of the one-carbon bridge. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)