Abstract
The basic method for the synthesis of dronic acid derivatives (etidronate, fenidronate, pamidronate, alendronate, ibandronate, zoledronic acid, and risedronic acid) starting from the corresponding carboxylic acid, phosphorus trichloride and phosphorous acid is surveyed. The focus is on the optimized syntheses elaborated by us using only 3.2 equivalents of phosphorus trichloride as the P-reagent in methanesulfonic acid as the solvent.