Natural pentacyclic triterpenoids are important secondary metabolites which have attracted interest due to the wide range of their biological activities such as antitumor1 antidiabetic2 anti-inflammatory3 and antiviral activities4. Betulin and betulinic, oleanolic, ursolic acids are the most recognizable compounds of this branch, which are isolated from various plants. However, the medicinal application of these natural products are hindered by their extremely low water solubility and thus – low bioavailability.5 One option to overcome this limitation is introduction of polar anionic functional groups such as phosphates and sulfates, which, however, are prone to hydrolysis. Here we describe the synthesis of novel anionic triterpenoid phosphonates, which bear methylene-bridged phosphonate side chains. The latter are suitable for both the enhanced water solubility and complexing / salt formation with metal ions like Ca2+, which is important for their further applications as bioactive additives to various calcium phosphate-based biomaterials