Figure 2

Structure-activity relationship of monastrol derivatives. (A) Scheme depicting the Biginelli condensation, a one-pot reaction for preparing monastrol derivatives [40]. (B) Monastrol (circles), but not derivative 2 (squares), inhibits ATP hydrolysis by 500 nM hEg5-367H in KC25 buffer supplemented with 1 mM ATP-KOH (pH 7.0). The IC₅₀ for monastrol is 5.2 +/- 0.4 μM. Each data point is the average of three independent experiments. (C) Summary of SAR results for monastrol derivatives inhibiting the catalytic activity of the Eg5 motor domain and inducing monoaster formation in tissue culture cells, as described [28]. IC₅₀ for each inhibitor was measured as described in part B. In cell-based assays, the potency of each derivative was obtained by treating BS-C-1 cells as described in the methods section, and manually counting mitotic cells to yield a score as follows: the drug concentration with roughly equal monastral and bipolar spindles, of < 50 μM (+++), weak compounds 50 to 200 μM (+ or ++), and inactive (-) compounds displayed no effect at 200 μM. Each cell-based assay was performed in duplicate.