Concomitant pseudopolymorphs of 10-deacetyl baccatin III.

Three new solvates [mono-dimethyl sulfoxide (mono-DMSO), mono-dimethyl acetamide (mono-DMA) and mono-dimethyl formamide (mono-DMF)] of 10-Deacetyl baccatin III, were generated by slow evaporation in DMSO, DMF, and DMSO/DMA (1:1) solvent systems respectively. Two concomitant forms mono-DMSO(a new form) and di-DMSO (a known form) were obtained in the DMSO solvent system. Yet two other concomitant forms mono-DMA (a new form) and di-DMSO (a known form) were obtained in DMSO/DMA (1:1) solvent system. A fourth solvate mono-DMF (a new form) was crystallized in unimolar ratio using DMF as a solvent. These solvates were characterized using powder X-ray diffraction, differential scanning calorimeter, thermogravimetric analysis (TGA), and spectroscopic [(13)C solid-state nuclear magnetic spectroscopy, solution (1)H NMR, and Fourier transform infrared] techniques. The interactions between host and guest molecules were elucitated by single-crystal X-ray diffraction data. In all the cases, guest molecules are connected to the host molecules by O-H∙∙∙O hydrogen bonds. A remarkable difference in the desolvation onset temperatures of di- and mono-DMSO solvates was observed which was also featured by a corresponding weight loss during TGA analysis.