| abstract |
An improved process is described for the preparation of 4-amino-1-hydroxybutylidene-1,1-bisophosphonic acid (ABP) or salts thereof which comprises: n (a) reacting 4-aminobutyric acid with a mixture of phosphorous acid and PCl 3 in the presence of methanesulfonic acid; n (b) contacting the mixture from Step (a) with an aqueous hydrolysis mixture, wherein the pH is maintained in the range of 4 to 10 during the contacting; and n (c) recovering said 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid or salts thereof. |