Synthetic Route Development for the Laboratory Preparation of Eupalinilide E.

Following the discovery that the guaianolide natural product eupalinilide E promotes the expansion of hematopoietic stem and progenitor cells; the development of a synthetic route to provide laboratory access to the natural product became a priority. Exploration of multiple synthetic routes yielded an approach that has permitted a scalable synthesis of the natural product. Two routes that failed to access eupalinilide E were triaged either as a result of providing an incorrect diastereomer or due to lack of synthetic efficiency. The successful strategy relied on late-stage allylic oxidations at two separate positions of the molecule, which significantly increased the breadth of reactions that could be used to this point. Subsequent to C-H bond oxidation, adaptations of existing chemical transformations were required to permit chemoselective reduction and oxidation reactions. These transformations included a modified Luche reduction and a selective homoallylic alcohol epoxidation.

Synthesis of Eupalinilide E, a Promoter of Human Hematopoietic Stem and Progenitor Cell Expansion.

Improving the ex vivo and in vivo production of hematopoietic stem and progenitor cells (HSPCs) has the potential to address the short supply of these cells that are used in the treatment of various blood diseases and disorders. Eupalinilide E promotes the expansion of human HSPCs and inhibits subsequent differentiation, leading to increased numbers of clinically useful cells. This natural product represents an important tool to uncover new methods to drive expansion while inhibiting differentiation. However, in the process of examining these effects, which occur through a novel mechanism, the natural product was consumed, which limited additional investigation. To provide renewed and improved access to eupalinilide E, a laboratory synthesis has been developed and is reported herein. The synthetic route can access >400 mg in a single batch, employing reactions conducted on useful scales in a single vessel. Key transformations enabling the approach include a diastereoselective borylative enyne cyclization and a late-stage double allylic C-H oxidation as well as adapted Luche reduction and aluminum-mediated epoxidation reactions to maximize the synthetic efficiency. Retesting of the synthetic eupalinilide E confirmed the compound's ability to expand HSPCs and inhibit differentiation.