Patent ID: 7002014
Filing Date: 2006-02-21
Classification: C07F

Abstract:
1. A process for preparing 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid salt in the hemipentahydrate crystal form, said process comprising the steps of: a) dissolving in an admixture of isopropyl alcohol and water, 3-pyridyl-1-hydroxyethylidene-1, 1-bisphosphonic acid and an inorganic base in sufficient amount to provide a pH of 6, to form a solution; b) heating the solution from about 50° C. to about 60° C. to form a heated solution; c) filtering said heated solution to form a filtered solution; d) adjusting the pH of said filtered solution with an inorganic acid to a pH range of from 4.7 to 5 while maintaining the temperature at the level oblained in step (b) to form a neutralized solution; e) cooling the neutralized solution to a temperature of about 20° C. to about 40° C. to form a nucleating slurry of 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid salt; f) adding to said slurry isopropyl alcohol and sufficient inorganic acid to provide a pH of from 4.7 to 5.2 to form a ripened slurry of 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid salt in the hemipentahydrate crystal form; and g) isolating 3-pyridyl-1-hydroxyethylidene-1,1-bisphosphonic acid salt hemipentahydrate.