SYNTHESIS OF α-HALOGENATED METHANEDIPHOSPHONATES1a, b

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Abstract
Methanediphospnonate (MDP) anions can exhibit anti-viral activity, inhibit bone resorption, and act as ligands in radiopharmaceuticals. α-Halo-substitution provides MDP derivatives (XYMDP, where × = H, F, CI or Br; Y = F, Cl or Br) with modified acid-base, steric and other properties. These compounds are conveniently made from the corresponding α-halogenated XYMDP esters (RO)2P(O)CXYP(O)(OR)2. Detailed procedures are given for synthesis of R4 XYMDP for R = Pri and X, Y = H. Cl; Cl, Cl; H, Br; Br, Br; F, Cl; F, Br and Cl, Br in 88–96% yield; for R = Et and X, Y = H, Cl; Cl. Cl; H, Br; Br, Br and Cl, F in 81–94% yield; and for R = Me and X, Y = Cl, Cl and Br, Br in 72–80% yield. NMR data (1H, 31P, 13C. (19F)) are presented for the products obtained. The XYMDP acids (X, Y = H, Cl; Cl, Cl; H, Br; Br, Br; F, Cl; F, Br and Cl, Br) were prepared by HCl hydrolysis of a corresponding ester and characterized as tris(dicyclohexylammonium) salts by elemental analyses and 31P NMR.