Towards the total synthesis of Stawamycin. Synthesis of C11-C21 fragment

the carbocyclic (c11-c21) fragment of stawamycin has been prepared by a sequence involving 11 steps (10% overall yield) from methyl (r)-(-)-3-hydroxy-2-methylpropionate. key steps are pd-catalyzed stille coupling reaction between a vinyl iodide and a vinylstannane followed by an intramolecular diels-alder cycloaddition reaction to afford the desired adduct as the major isomer together with three other possible adducts in 78% overall yield.