Preparation of some diaminoalkylphosphonic acids

Four diaminoalkylphosphonic acids (I) and their N-Benzoyl [see Proquest PDF for equation (I)] derivatives were synthesized, utilizing a modified Curtius reaction. The successful synthesis of this series of compounds provided an additional test of the generality of this method. The diamino phosphonic acids prepared were 1,2-diaminoethyl-(I, x=1); 1,3-diaminopropyl-(I, x=2); 1,4-diaminobutyl-(I, x=3) and 1,5-diaminopentylphosphonic acids (I, x=4). Two of the diamino phosphonic acids were analogs of naturally occurring amino carboxylic acids. These acids were 1,4-diaminobutylphosphonic acid (analog of ornithine) and 1,5-diaminopentylphosphonic acid (analog of lysine). Approximate pK values for these diamino phosphonic acids were determined from potentiometric titrations of these compounds. Three esters (III) synthesized were previously unreported. [see Proquest PDF for equation (III)] These esters (III) were tetraethyl 2-phosphonoglutarate (III, x=2); tetraethyl 2-phosphonoadipate (III, x=3) and tetraethyl 2-phosphonopimelate (III, x=4)