Patent ID: 8507449

Claim:
An aqueous phase process for the preparation of D-isoglutamyl-D-tryptophan, free of inorganic salts, which process comprises the following steps: (a) preparing a solution of H-D-iGlu-D-Trp-OH acid addition salt in an aqueous medium essentially free of organic solvent; or preparing a solution of H-D-iGlu-D-Trp-OH base addition salt in an aqueous medium essentially free of organic solvent; (b) adjusting the pH to from about 2.0 to about 3.2 with an alkali metal hydroxide solution or a mineral acid solution, to cause the precipitation of H-D-iGlu-D-Trp-OH; (c) recovering the precipitated H-D-iGlu-D-Trp-OH thereof; and (d) vacuum drying the product resulting from step (c) to give H-D-iGlu-D-Trp-OH.