Abstract: This invention relates to a method for preparing azithromycin dihydrate from crude azithromycin by the gradual crystallization of azithromycin from acetone by the addition of a minimal amount of water to effect crystal formation is disclosed. This invention also relates to a method of making azithromycin from desmethyl-azithromycin by dissolving desmethyl-azithromycin in acetone, adding activated carbon, adding formaldehyde, adding formic acid; refluxing the desmethyl-azithromycin acetone solution, adding sodium hydroxide to induce precipitation of azithromycin, and isolating azithromycin.

Abstract: There is disclosed a method of converting gabapenting hydrochloride substantially free of inorganic salts to gabapenting form II. The method comprises the steps of: (1) obtaining gabapentin hydrochloride that is substantially free of inorganic salts; (2) mixing a solution of the gabapenting hydrochloride with an additional amine in a first solvent so as to obtain a precipitate comprising gabapenting; and then (3) recovering gabapentin form II from the precipitate. The precipitated gabapentin is a novel polymorphic form of gabapentin possessing a crystalline structure characterized by novel sets of peaks in the powder X-ray diffraction pattern and in the FTIR spectra. This newly disclosed polymorph of gabapentin is characterized herein as gabapentin form III.