Scalable Total Synthesis of (+)-Desmethylxestospongin B.

Abstract

Herein, the execution of synthetic strategies solving scalability issues observed in the original route is reported, increasing the total yield by 50% compared to the previously disclosed synthesis. A notable restructuring of the route's initial steps to reach a common allylic alcohol intermediate employs a highly stereoselective epoxidation method and avoids superfluous protecting group manipulations while limiting dependence on kinetic resolution in establishing stereochemistry for four of the six chiral centers in (+)-desmethylxestospongin B. Different protecting group strategies to avoid problems with their subsequent removal were considered and enacted; to this end, material was retained as byproducts were suppressed. While the lactam semireduction under Birch conditions requires further investigation, the updated synthesis of (+)-desmethylxestospongin B reported here made it more scalable, affording 0.37 g of this natural product for continued biological studies.