A Divergent Enantioselective Strategy for the Synthesis of Griseusins

The first enantioselective total synthesis of griseusin A, griseusin C, 4′-deacetyl-griseusin A, and two non-native counterparts in 11–14 steps is reported. This strategy highlights a key hydroxy-directed CH olefination of 1-methylene isochroman with an α,β-unsaturated ketone followed by subsequent stereoselective epoxidation and regioselective cyclization to afford the signature tetrahydro-spiropyran ring. Colorectal cancer cell cytotoxicities of the final products highlight the impact of the griseusin tetrahydro-spiropyran ring on bioactivity. As the first divergent enantioselective synthesis, the strategy put forth sets the stage for further griseusin mechanism-of-action and SAR studies.