Patent ID: 6844449

Claim:
A process for the production of a modification A of compound I characterized by the X-ray diffraction pattern in which reflections not coinciding with the reflections of the other modifications are observed inter alia at 14.87°2θ20(5.96 Å), 19.99°2θ(4.44 Å), 20.88°2θ(4.25 Å), 22.78°2θ(3.90 Å), 24.53°2θ(3.63 Å), 25.66°2θ(3.47 Å), 30.05°2θ(2.97 Å) and at 37.29°2θ(2.41 Å), and modification B of the compound I characterized by the X-ray diffraction pattern in which reflections not coinciding with the reflections of the other modifications are observed inter alia at 13.80°2θ(6.41 Å), 15.22°2θ(5.82 Å), 17.50°2θ(5.06 Å) and at 23.48°2θ(3.79 Å) as well as of A/B mixtures of arbitrary composition by reacting R-thioctic acid with trometamol, wherein trometamol is metered into a solution of R-thioctic acid in a polar solvent, the suspension is heated until the trometamol has dissolved, and is then crystallized by cooling.