Selective synthesis of (2Z,4E)-dienyl esters by ene-diene cross metathesis

reaction: see text] Cross metathesis of terminal alkenes with methyl (2Z,4E)-hexadienoate and related dienyl esters provides substituted (2Z,4E)-dienyl esters in good yields. Small-scale reactions are effectively promoted by the standard second-generation Grubbs-Hoveyda catalyst (GH-II), while a new fluorous GH-II catalyst is used for separation and recovery in gram-scale reactions. The transformation is featured in a rapid synthesis of the bottom fragments of the potent anticancer agents (-)-dictyostatin and 6-epi-dictyostatin.