Stereoselective total synthesis of (+)-giganin and its C10 epimer by using late-stage lithiation-borylation methodology.

The first total synthesis of (+)-giganin and its unnatural diastereoisomer (+)-C10-epi-giganin has been completed in a total of 13 linear steps, and 7 % and 8 % overall yield, respectively (see scheme; (-)-sp= (-)-sparteine, (+)-sps=(+)-sparteine surrogate). Lithiation-borylation methodology has been successfully applied in the key step, to couple together advanced intermediates with very high diastereoselectivity, thus demonstrating its power as a tool for total synthesis.