Patent ID: 8592607

Claim:
A process for the preparation of crystalline mono-sodium salt of D-isoglutamyl-D-tryptophan, wherein the process comprises the steps of: (a) preparing a solution of D-isoglutamyl-D-tryptophan and sodium hydroxide in water at a pH of about 6.5 to about 7.2; (b) filtering the solution to remove solid particulates; (c) evaporating the water to concentrate the filtrate; and (d) adding isopropanol to precipitate the crystalline mono-sodium salt of D-isoglutamyl-D-tryptophan, or steps (a) and (b) followed by the steps of: (e) stirring the solid obtained from process steps (a), (b), (c), and (d) with ethyl acetate; and (f) filtering the solid, or steps (a) and (b) followed by the steps of: (g) evaporating the filtrate from step (b) to give a solid; (h) adding water to obtain a solution of the mono-sodium salt of D-isoglutamyl-D-tryptophan; and (i) evaporating the water over a period of more than about 5 hrs to give the crystalline mono-sodium salt of D-isoglutamyl-D-tryptophan, or (j) preparing a solution of the mono-sodium salt of D-isoglutamyl-D-tryptophan in methanol; (k) filtering the solution to remove solid particulates; and (l) adding isopropanol to precipitate the crystalline mono-sodium salt of D-isoglutamyl-D-tryptophan, or (m) preparing a solution of the mono-ammonium salt of D-isoglutamyl-D-tryptophan and sodium hydroxide in water; followed by steps (b), (c) and (d).