Comparison of the crystal structures of the potent anticancer and anti-angiogenic agent regorafenib and its monohydrate

摘要

Regorafenib {systematic name: 4-[4-({[4-chloro-3-(trifluoromethy)phenyl]car-bamoyl}amino)-3-fluorophenoxy]-1-methylpyridine-2-carboxamide}, C21H15Cl-F4N4O3, is a potent anticancer and anti-angiogenic agent that possesses various activities on the VEGFR, PDGFR, raf and/or flt-3 kinase signaling molecules. The compound has been crystallized as polymorphic form I and as the mono-hydrate, C2iHisClF4N4O3-H2O. The regorafenib molecule consists of biarylurea and pyridine-2-carboxamide units linked by an ether group. A comparison of both forms shows that they differ in the relative orientation of the biarylurea and pyridine-2-carboxamide units, due to different rotations around the ether group, as measured by the C—O —C bond angles [119.5 (3)° in regorafenib and 116.10 (15)° in the monohydrate]. Meanwhile, the conformational differences are reflected in different hydrogen-bond networks. Polymorphic form I contains two intermolecular N—H ? -O hydrogen bonds, which link the regorafenib molecules into an infinite molecular chain along the b axis. In the monohydrate, the presence of the solvent water molecule results in more abundant hydrogen bonds. The water molecules act as donors and acceptors, forming N—H ? -O and O—H- ? O hydrogen-bond interactions. Thus, R24(28) ring motifs are formed, which are fused to form continuous spiral ring motifs along the a axis. The (trifluoromethyl)phenyl rings protrude on the outside of these motifs and interdigitate with those of adjacent ring motifs, thereby forming columns populated by halogen atoms.