Toward an Improved Triterpene 3- O-Glucuronidation: The Systematic Determination of the Relative Reactivities of Glucuronyl Donors and Acceptors

J Org Chem. 2023 Jul 21;88(14):9946-9958. doi: 10.1021/acs.joc.3c00709. Epub 2023 Jul 6.

Abstract

3-O-β-Glucuronide triterpenes are plant-derived compounds. Some of them have been used as herbal medicine and in pharmaceuticals, such as chikusetsu saponins and Quillaja saponins. However, the demand for these materials has remained largely a challenge owing to their natural scarcity and low-yielding purification process. Therefore, a chemical triterpene 3-O-glucuronidation was conducted in this study to alleviate the surging demand on natural source. Various glucuronyl imidate donors and oleanane-type triterpene acceptors were synthesized, and the relative reactivity values (RRV) and acceptor nucleophilic constants (Aka) were systematically measured to study their influence on glucuronidation yield. As a result, applying donors in higher RRV value generally improved the production of 3-O-glucuronide triterpenes. Meanwhile, a bulky pivaloyl group was an ideal 2-O-protection to provide β-selectivity and prevented side reactions, including orthoester formation and acyl-transfer reaction. Collectively, a positive correlation was observed between reactive donors/acceptors and improved glucuronidation yields. These findings offered insights on the influence of donors' and acceptors' reactivities on 3-O-β-glucuronide triterpenes synthesis, and this knowledge would help to access saponins of interest to address future needs.

MeSH terms

  • Glucuronides
  • Plant Extracts / chemistry
  • Plants, Medicinal* / chemistry
  • Saponins* / chemistry
  • Triterpenes* / chemistry

Substances

  • Triterpenes
  • Glucuronides
  • Saponins
  • Plant Extracts