NOVEL PROCESS FOR PREPARING RISEDRONIC ACID

摘要

The present invention relates to a process for preparing risedronic acid comprising the step of combining a 3-pyridyl acetic acid or a salt thereof, phosphorous acid, and a halophosporous compound selected from PCl3, PCI5, POCl3, PBr3, POBr3, and PBr5 in the presence of a diluent that is either a bicyclic aliphatic hydrocarbon or a substituted cyclic aliphatic hydrocarbon or a mixture thereof, in combination with a codiluent, that is orthophosphoric acid.