Total Synthesis of Zephycarinatines via Photocatalytic Reductive Radical ipso‐Cyclization

We report herein a nonbiomimetic strategy for the total synthesis of the plicamine‐type alkaloids zephycarinatines C and D. The key feature of the synthesis is a stereoselective reductive radical ipso‐cyclization using visible‐light‐mediated photoredox catalysis. This cyclization enabled the construction of a 6,6‐spirocyclic core structure through the addition of a carbon‐centered radical onto the aromatic ring. Biological evaluation of zephycarinatines and their derivatives revealed that the synthetic derivative with a keto group displays moderate inhibitory activity against LPS‐induced NO production. This approach could offer future opportunities to expand the chemical diversity of plicamine‐type alkaloids as well as providing useful intermediates for their syntheses. Total synthesis of the plicamine‐type alkaloids, zephycarinatines C and D has been achieved. The key feature of the synthesis is a stereoselective radical ipso‐cyclization using visible‐light‐mediated photoredox catalysis. Biological evaluation of zephycarinatines and their derivatives revealed that a synthetic derivative displays moderate inhibitory activity against LPS‐induced NO production.