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Some geminal bisphosphonates are used clinically for a number of important bone/calcium related diseases; however, side effects and lack of selectivity impede their wide use. This work reports the synthesis and evaluation of bisacylphosphonates (e.g., adipoyl- and suberoylbisphosphonate). These compounds were found to inhibit significantly hydroxyapatite formation and dissolution in vitro and the calcification of bioprosthetic tissue implanted subdermally in rats. These are the first instances of nongeminal bisphosphonates [P-(C)n-P, n greater than or equal to 2] that have been reported to be active in calcium-related disorders. The reported bisacylphosphonates possess apparent lower toxicity, and their calcium complexes/salts have improved solubility properties. Therefore, they are of potential importance for clinical applications.

The biological effects of bisphosphonates in calcium-related disorders are attributed to the incorporation of the bisphosphonates in bone, enabling direct interaction with osteoclasts and/or osteoblasts. The high accumulation of bisphosphonates in bone, due to their high affinity to hydroxyapatite (HAP), is essential for mediating in vitro and in vivo activity. In this study we examined the activity of tetrakisphosphonates, molecules containing two P-C-P type bisphosphonate moieties connected by a carbon chain. The novel compounds were examined in a battery of in vitro and in vivo models including HAP formation and dissolution, ectopic calcification, bone resorption, tumor osteolysis, and of macrophage-like cells (anti- or pro-inflammatory properties). The inhibition of ectopic calcification was ranked as follows: geminal bisphosphonates > bisacylphosphonates > tetrakisphosphonates. Pamidronate, but not the tetrakisphosphonates, was an effective antiosteolytic agent. Neither DNTP (tetrasodium 1,9-dihydroxynonane 1,1,9,9-tetrakisphosphonate) nor the bisacylphosphonate, PiBP (pimeloylbisphosphonate) seem to possess strong macrophage suppressive or inductive effects and can be considered to be relatively inactive in terms of anti- or pro-inflammatory action. A significant anticalcification effect was caused by various phosphonates, such as the tetrakisphosphonates, but DNTP, a tetrakisphosphonate, was found toxic as it impeded somatic growth and bone development.

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Reaction of methyl benzoylphenylphosphinate 1 with hydroxylamine gave methyl a-hydroxyiminobenzylphenylphosphinate 2 as a mixture of €and Z isomers with the E isomer predominating. Pure ( E ) -2 when heated gave methyl N-benzoylphenylphosphonamidate 3 as the sole product. In contrast, (Z) -2 when heated gave, as a result of fragmentation, mainly methyl hydrogen phenylphosphonate 4 and benzonitrile, together with methyl N-phenylcarbamoylphenylphosphinate 5 as the minor product; the latter results from Beckmann rearrangement of (2)-2. Analogous behaviour is exhibited by the two geometrical isomers of dimethyl a-hydroxyiminobentylphosphonate 8. The crystal structures of methyl ( E ) -a-hydroxyiminobenzylphenylphosphinate ( E ) -2 and methyl benzoylphenylphosphonamidate 3 are reported.Recently we reported initial results from our study concerning the oxyiminophosphonic functional group. ' Our interest in this