Protecting-Group-Free Total Synthesis and Biological Investigation of Cabucine Oxindole A†

Main observation and conclusion Owing to their challenging structures and promising biological profiles, spirooxindole alkaloids have long attracted much attention from the synthetic community. Herein, we wish to describe a concise, protecting-group-free total synthesis of cabucine oxindole A, a putative natural spirooxindole alkaloid and a possible biosynthetic congener of cabucine and palmirine. Key transformations of our approach include a one-step, organocatalytic and enantioselective construction of the spiro[pyrrolidine-3,3'-oxindole] moiety and a Korte rearrangement to furnish the final dihydropyran motif. Biological investigation of 1 and its synthetic intermediates revealed lactone 2 as a mild MOLT-4 and MCF7 cell line inhibitor.

Automated summary

This study presents a concise, protecting-group-free total synthesis of cabucine oxindole A, a putative natural spirooxindole alkaloid, and investigates the biological activity of its synthetic intermediates.