Isostructurality Among Solvates of Cabazitaxel: X-ray Structures and New Solvates Preparation

Cabazitaxel is an anticancer drug and its marketed product (form A) is acetone solvate (1:1) (Didier E, Perrin MA. 2005. Patent WO2005/028462 A1). This work describes three crystal structures of cabazitaxel 1:1 solvates with isopropyl alcohol (B), 2-butanol (C), and dioxane (D). These solvates are isostructural with cabazitaxel forming a host framework through hydrogen bonds and the guest solvent molecules located in channels from which they can escape. The host is hydrogen bonded to each other through hydroxyl O1 and sec-amide N3′, whereas the hydroxyl O2′ plays an important role in connecting the host to the guest. Moreover, because of the existence of channels in the crystal structure, the solvent-replacement method was established to prepare four new solvates of cabazitaxel with dimethyl formamide (E), cyclohexane (F), n-hexane (G), and ethyl ether (H). All the seven solvates involved in this work were proven to be isostructural by methods of X-ray crystallography and contain the same amount of solvents by thermogravimetric analysis. The single-crystal structures of solvate C-E and the solvates prepared by solvent-replacement method have been reported for the first time.