The solid-phase combinatorial synthesis of β-thioketones

A solid-phase split-mix organic synthesis method was developed which, by two synthetic steps, converts polymer-bound aldehyde I into resins III. Step one consists of dividing I into three equal portions in separate flasks, condensing each with a different ylide, and subsequently recombining to give II. This mixture of beads was again equally divided into three flasks, and each flask treated with a thiolate Michael donor. Prior to recombining the contents of each flask (i.e., sub-library), samples of each resin were removed and incubated with a THF/HCO₂H mixture to liberate the small molecule products. GC-MS established that each sub-library (A, B, and C) contained the three anticipated formate esters. In addition, GC analysis illustrates that, while there were no purification steps involved in this solid-phase analogous organic synthesis save bead washings between steps, the desired products are obtained in excellent purity. Single bead (200-400 mesh) selection from library D (combined sub-libraries A-C), solvolysis, and GC-MS analysis shows that compound identities can be established on a per bead basis.