Strategy towards the enantioselective synthesis of schiglautone AThis work was carried out between March 2011 and December 2014 in the laboratory of Prof. Carreira at ETH Zürich and is part of the author's PhD thesis (C. Le Chapelain, ETH Zürich, April 2015, DOI 10.3929/ethz-a-010510664).Electronic supplementary information (ESI) available: Full experimental, copies of NMR spectra for all new compounds, SFC chromatograms. See DOI: 10.1039/c7ob00766c

Herein is described a convergent enantioselective route to an advanced intermediate in the synthesis of schiglautone A, a Schisandra triterpenoid with an unusual architecture. The synthetic route to this intermediate displaying 6 of the 7 stereocenters builds upon two fragments, an aldehyde elaborated from the Wieland-Miescher ketone, and a ketone. The preparation of the latter features a lithiation-borylation enzymatic resolution sequence, which led to the formation of the desired product with high enantio- and diastereoselectivities. After aldol coupling of the two fragments, the final quaternary stereocenter was installed by cyclopropane opening. The functionalized intermediate was isolated as a single diastereoisomer and thus offers a valuable starting point for further synthetic exploration. The enantioselective synthesis of a functionalized intermediate comprising 6 of the 7 stereocenters of schiglautone A is reported and features a lithiation-borylation enzymatic resolution sequence.