The outcomes of molecular docking and SPLIF analysis indicate that the interactions of compounds 2a and 3a with tubulin are predominantly hydrophobic, as with most existing colchicine ligands. In addition, each of the compounds 2a and 3a are predicted to form a single hydrogen bond between the Asp-249 amino acid of β-tubulin and the oxygen of the pyrrolidone ring. The validity of these predictions is justified by the very similar binding patterns of previously characterized ligands, whose tubulin-bound X-ray structures are available from the PDB (Fig. ). The higher binding ability of compound 3a compared to compound 2a is resulted from: a) fixation of the mutual arrangement of two aromatic groups in 3a, in contrast to that in 2a, wherein rotation around the bond between the C(5) atom of the pyrrolidone ring and the styryl moiety is possible; b) a more suitable dihedral angle between the two aromatic rings in 3a due to geometric constraints induced by the piperidine ring formation (Fig. ). Based on molecular modeling results (Fig. , S2), we hypothesized that compound 3c, possessing an additional hydroxy group at the meta-position of exocyclic phenyl substituent, might allow the formation of an additional hydrogen bond (Fig. ). Induced fit docking of compound 3c confirmed this idea, identifying a possible binding pose of that compound, which is similar to the predicted pose of 3a, but enhanced with hydrogen bonds with Asn-347 and Lys-350 of βtubulin (Fig. ). Encouraged by that prediction, we synthesized the compound 3c by the method described in Scheme 2. Using DIC microscopy in vitro assay, we visualized and quantified microtubule dynamics in the presence of compound 3c (Fig. ). At the concentration of 25 μM, this compound decreased the growth rate of microtubules by more than 50% and lowered the frequency of catastrophes (Fig. ).