Synthetic analogues of the microtubule-stabilizing sponge alkaloid ceratamine A are more active than the natural product

Desbromoceratamine A (3) exhibits significantly less potent activity than the natural product ceratamine A (1) in a cell-based assay for antimitotic activity. Synthesis of the ceratamine A analogue 4 has shown that replacing the bromine atoms in the natural product with methyl groups generates an analogue that is more active than natural ceratamine A (1). Further enhancement of the antimitotic activity of the ceratamine pharmacophore has been achieved in the synthetic analogue 33, which has both bromine atoms replaced with methyl groups and an additional methyl substituent on the amino nitrogen at C-2. An efficient synthetic route has been developed to 33 that should enable the first in vivo evaluation of the new ceratamine microtubule-stabilizing pharmacophore and has provided several additional analogues for structure-activity relationship evaluation.