Synthesis of thiazolo[4,5- <i>d</i> ]pyrimidine derivatives based on purine <i>via</i> solid-phase synthesis

Solid-phase synthesis was employed to construct a library of thiazolo[4,5-<i>d</i>]pyrimidine derivatives. The free amide at the 5-position of the thiazole, which was previously difficult to introduce <i>via</i> the Thorpe-Ziegler reaction, was successfully optimized in solid-phase synthesis using a 2,4-dimethoxy-substituted scaffold, and using iodine as a catalyst, the reaction with aldehyde successfully synthesized thiazolo-pyrimidinone derivatives. To synthesize thiazolo[4,5-<i>d</i>]pyrimidine derivatives, the direct amination reaction using BOP was successfully optimized. By applying the optimized conditions to solid-phase synthesis, a library of 36 derivatives was constructed, achieving average yields of 63-93% over six steps.