Scalable Asymmetric Total Syntheses of (+)-Psoracorylifol B and (+)-ent-Psoracorylifol C

The first, asymmetric total syntheses of potent antimicrobial Psoracorylifol B (>1.3 g obtained, dr 10.5:1) with a 9.4% overall yield on a gram scale in 14 steps and ent-Psoracorylifol C with a 4.3% yield in 16 steps were achieved. The key features of our synthesis include (i) sequential, rarely explored Achmatowicz rearrangement/bicycloketalization to construct the 6,8-dioxabicyclo[3.2.1]octane core, and (ii) Cu-mediated S(N)2' methylation or Johnson-Claisen rearrangement to stereoselectively install the all-carbon quaternary stereocenter. This concise, highly efficient, and scalable synthetic route may provide expedited and practical access to psoracorylifols and their analogues for further biological activity evaluation.