Synthesis of Quillaic Acid through Sustainable C–H Bond Activations

To meet the demand for quillaic acid, a multigram synthesis of quillaic acid was accomplished in 14 steps, starting from oleanolic acid, leading to an overall yield of 3.4%. Key features include C–H activation at C-16 and C-23. Through Pd-catalyzed C–H acetoxylation, the oxidation at C-23 was observed as the major product, as opposed to at C-24. A copper-mediated C–H hydroxylation using O2 successfully afforded the single isomer, 16β-ol triterpenoid, followed by configuration inversion to the desired 16α-ol compound. In summary, with steps optimized and conducted on a multigram scale, quillaic acid could be feasibly acquired through C–H activation with inexpensive copper catalysts, promoting a more sustainable approach.