Total Synthesis of ent-Lycoricidine via a Thiyl Radical Addition-Cyclization Sequence

摘要

Pancratistatin (1) and structurally related naturally occurring materials such as 7-deoxypancratistatin (2), narciclasine (3), and lycoricidine (4) have attracted considerable synthetic attention because of interest in the biological activity of these compounds and their novel structural aspects. In particular, three recent total syntheses of 1 have been recorded as have five total syntheses of 4. Our own efforts in this area have led to a recently reported synthesis of 2 via a radical cyclization-based strategy. We now report the development of a rather different radical based approach to 4. Although the approach is capable of providing either enantiomer of 4, we chose to pursue the synthesis of ent-4 to allow for biological assay of this material.