Crystalline form of betulin: polymorphism or pseudopolymorphism?

By recrystallization with different solvents as well as decomposition of betulin ethanol solvate at room temperature a new crystalline form of the biologically active compound betulin, namely hemihydrate of betulin, is obtained. By single crystal X-ray diffraction data the crystal structure of hemihydrate of betulin is determined. By powder X-ray thermodiffraction and differential scanning calorimetry it is found that when hemihydrate of betulin is heated to melting, Н₂О molecules are removed and solid-phase transformations occur, which are related to the formation of an intermediate crystalline form andan orthorhombic modification of betulin.