A diosphenol-based strategy for the total synthesis of (-)-terpestacin

A novel diosphenol-based strategy has been developed for the enantioselective synthesis of (-)-terpestacin by multiple usage of the alpha-diketone functionality, first in the Pd AAA-Claisen rearrangement protocol, and second by the employment of its oxidized form, the ene-1,2-dione, as an excellent Michael acceptor. This synthesis demonstrates that the sequence of O-allylation-Claisen rearrangement provides a chemo- and regioselective enolate allylation, which can be performed asymmetrically with respect to the enolate or allyl fragment or both. In addition, many interesting chemoselectivity issues, including a highly selective RCM and a dihydroxylation, have been addressed. Overall, this synthesis was accomplished in 20 longest linear steps (24 total steps) from the inexpensive and commercially available 3-methyl-1,2-cyclopentanedione.