Different pathways for the deoxygenation of the A-ring of natural triterpene compounds
作者:Andres Parra、Pilar E. Lopez、Andres Garcia-Granados
DOI:10.1080/14786410903172098
日期:2010.1.20
Some deoxygenation pathways were tested to remove the hydroxyl groups of the natural triterpenes oleanolic acid and maslinic acid to obtain a practical starting material for the semisynthesis of other interesting organic synthons. Different deoxygenation processes were carried out starting from these triterpenic acids or from several derivatives such as methyl esters and epoxy derivatives. The hydroxyl groups were transformed into some intermediate compounds including xanthyl, thiocarbonyl or tosyl derivatives. The opening of the oxirane ring between C-2 and C-3 was also achieved through different methods using deoxygenating reagents such as Me3SiCl/NaI, WCl4/n-BuLi and Cp2TiCl.
Triterpenoid Hydroxamates as HIF Prolyl Hydrolase Inhibitors
Pentacyclic triterpenoid acids (PCTTAs) are pleiotropic agents that target many macromolecular endpoints with low to moderate affinity. To explore the biological space associated with PCTTAs, we have investigated the carboxylate-to-hydroxamate transformation, discovering that it de-emphasizes affinity for the transcription factors targeted by the natural compounds (NF-kappa B, STAT3, Nrf2, TGRS) and selectively induces inhibitory activity on HIF prolyl hydrolases (PHDs). Activity was reversible, isoform-selective, dependent on the hydroxamate location, and negligible when this group was replaced by other chelating elements or O-alkylated. The hydroxamate of betulinic acid (Sb) was selected for further studies, and evaluation of its effect on HIF-la expression under normal and hypoxic conditions qualified it as a promising lead structure for the discovery of new candidates in the realm of neuroprotection.