A cell-permeable 2'-benzyloxy griseofulvin derivative that displays enhanced mammalian cancer-selective toxicity (IC50 ≤2, ≤4, ≤12, and ≥30μM against panels of leukemia, myeloma, solid tumors, and non-malignant cell lines, respectively), but little antifungal activity, by activating spindle-assembly-checkpoint without affecting microtubule kinetochore attachm