A comparative study of boron-containing and boron-omitted capsaicinoids

This study reports the synthesis and characterization of a limited number of novel boron-containing and boron-omitted capsaicinoids, providing 12 unique substrates. We have previously reported boron-containing capsaicinoids that showed improved bioactivity compared to capsaicin itself but have yet to test a series of analogous boron-omitted substrates as a direct comparison. The boron-containing capsaicinoids bear a pinacolboronate ester (Bpin) group, which was incorporated using an iridium-catalyzed hydroboration reaction. We report that although nearly all compounds display moderate cytotoxic activity that bests that of capsaicin against human colon HCT116 cancer cells, the activity of our boron-omitted capsaicinoids surpasses that of the boron-containing analogues.