Synthesis of a NaturalProduct-Based 5<i>H</i>‑Thiazolo[5′,4′:5,6]pyrido[2,3‑<i>b</i>]indole Derivative via Solid-Phase Synthesis

The solid-phase synthesis method is optimized for building chemical libraries. Furthermore, chemical libraries are essential tools in drug discovery used to identify hit compounds. We constructed a 5<i>H</i>-thiazolo[5′,4′:5,6]pyrido[2,3-<i>b</i>]indole derivative library using solid-phase synthesis. The indole insertion reaction at the benzylic position using a Lewis acid and the oxidative cyclization reaction using iodine were used for synthesis. Using optimized solution-phase reaction conditions, a solid-phase synthesis method comprising a total of eight steps was employed to build a 5<i>H</i>-thiazolo[5′,4′:5,6]pyrido[2,3-<i>b</i>]indole derivative library. In addition, we found an efficient compound library synthesis route with each synthetic step having a yield of 62–82%.