Crystal Structure of Aspartame Anhydrate from Powder Diffraction Data. Structural Aspects of the Dehydration Process of Aspartame

Aspartame has three pseudo-polymorphic forms, two hydrates and a hemi-hydrate, for which crystal structures were
determined from single-crystal diffraction data. This paper presents the crystal structure of the anhydrate, which was obtained by
dehydrating the hemi-hydrate. The crystal structure of aspartame anhydrate, l-aspartyl-l-phenylalanine methyl ester, was determined
from X-ray powder diffraction data. Aspartame anhydrate crystallizes in the monoclinic system with space group P21 and cell
parameters:  a = 19.4078(10) Å, b = 4.9605(2) Å, c = 15.6547(9) Å, β = 94.876(2)°, V = 1501.65(14) Å3. Final Rietveld refinement
resulted in Rwp = 2.26 and a GOOF of 2.30. Comparing the hydrates of aspartame and using molecular modeling provide a complete
and clear picture of the dehydration behavior of aspartame at the molecular level.