Synthesis of M₄IDP and Optimum Labeling Conditions of ⁹⁹Tc^m-M₄IDP

1-Hydroxy-2-（4-methyl-1H-imidazoleyl）-ethylidene-1,1-bisphosphonic（M₄IDP）was prepared by three steps of N-alkylation、ester hydrolation and phosphoric acid acylation from the raw material 4-methyl-1H- imidazole. The structures of intermediate and target compounds were identified by Elemental Analysis、IR、MS and ¹H NMR. Then M₄IDP was directly labeled by Na⁹⁹Tc^mO₄ to afford ⁹⁹Tc^m-M₄IDP. The results showed that the best labeling conditions were 30 minutes reaction time， pH 6，100 μg SnCl₂·2H₂O， and 5 mg M₄IDP. In this condition, the labeling yield was more than 95% and ⁹⁹Tc^m-M₄IDP showed good biological stability in vitro.