The Devil is in the Detail: A Rare H-Bonding Motif in New Forms of Docetaxel

Abstract

Docetaxel is a semisynthetic analog of the taxane paclitaxel, pivotal for the treatment of various types of cancer. Minor differences in its chemical structure give docetaxel a slightly better water solubility profile when compared to paclitaxel. An understanding of the hydrogen-bonding network in docetaxel is therefore imperative if an explanation for its improved solubility over its predecessor is to be sought. New crystalline forms for solvated (ethanol), hydrated, and anhydrous docetaxel are reported. The crystal structures were determined by single crystal synchrotron and laboratory powder X-ray diffraction experiments on crystalline materials resulting from polymorph screening tests in various solvents. Variable-temperature experiments were carried out over ranges between 20 and 130 °C, with subsequent loss of crystal water at 70 and 90 °C. The resulting structures are discussed in terms of their intermolecular interactions, molecular conformations, and packing motifs. A rare hydrogen-bonding motif,...