Formation of stereochemically defined exocyclic double bonds, present in a number of natural products, can possess a considerable synthetic challenge.Herein we disclose an efficient, stereoselective synthesis of (S,E) ethylidene proline derivative 2  via a boron enolate Ireland-Claisen rearrangement of 7-membered lactone 1 , and the further elaboration of this building block into Barmumycin and Limazepine E  . The synthesis of 7-membered lactone 1  from (S)-methyl lactate, the optimization studies of the key transformation � the Ireland-Claisen rearrangement and the completion of total syntheses will be presented.

Application of chelation controlled Ireland-Claisen rearrangement in the total syntheses of Barmumycin and Limazepine E

245th National Meeting (2013)

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