Series To Phosphonic Acid Derivatives Synthesis, Osseous And Antitumor Activity

The antiresorption ability and high bone affinities of bisphosphonic acids were found in1969, and bisphosphonic acids are now the most widely used clinically drugs for the treatment of various metabolic bone diseases. They were showed potent direct anti-tumour effects in the past a few years. Zoledrionic acid (Zol), a kind of the typical third generation bisphosphonic acids, exhibits high bone affinity and high potent anti-tumour activity. In this work, we start to optimize its structure for the purpose of developing novel bisphosphonic acids with excellent biological properties.In this work, a series of novel zoldedronic acid derivatives,1-hydroxy-6-(1H-imidazol-1-yl) hexane-1,1-bisphosphonic acid (3a),1-hydroxy-6-(2-methyl-1H-imidazol-1-yl) hexane-1,1-bisphosphonic acid (3b),1-hydroxy-6-(2-ethyl-1H-imidazol-1-yl)hexane-1,1-bisphosphonic acid (3c),1-hydroxy-6-(2-propyl-1H-imidazol-1-yl)hexane-1,1-bisphosphonic acid (3d) and1-hydroxy-6-(2-butyl-1H-imidazol-1-yl) hexane-1,1-bisphosphonic acid (3e), were synthesized from relevant raw materials by three steps. The isolation of the target compounds was optimized to get higher yields. The structures were charactered by elemental analysis, IR, Mass Spectrometry and’H-NMR. Single crystals were cultivated in solution (slow avaportion or cooling), and their structures were determined by X-ray diffraction method for preliminary investigation of their conformations.The amount of these five targeted compounds binding to hydroxyapatite was determined by HPLC method in aqueous solution. The investigations show that the more compound is added to the solution, the faster adsorption equilibrium will get, and the maximum bound amount gets larger and reaches constant level finally. The binding behavior is also affected by the pH value of the solution. The maximum binding amount of compound3b on HA was130μmol/g, while no saturation was shown for Zol under acidic condition. At pH7.4, the maximum binding amount of compound3b was115μmol/g, while it was142μmol/g for Zol. It can speculate that the binding affinity of3b was highest among the derivatives, and it will retain on bone for longer period of time because the maximum binding amount was larger than the other.The bisphosphonic acids were used to treat human osteosarcoma U2-OS cell line, and cell growth inhibition in vitro was assessed by MTT method. The results show that half inhibitory concentration IC50values were341,429,511,534and755μM for3a,3b,3c,3d,3e, respectively. It indicates that these bishosphonic acids have weak effect of inhibiting proliferation of human osteosarcoma U2-OS cell line. When the alkyl group on the C-2 postion of the imidazole group in the molecular becomes larger, the growth inhition ability becomes weaker gradually.