Methyl on Tropone of MTC (MT-MTC, 4, Figure ), Methyl on Benzene of MTC (MT-MTC, 5), and DiMethyl MTC (DM-MTC, 6). Through the course of these studies, we identified a highly configurationally stable AC ring analogue, (aR)-6, that has tubulin-inhibition and antiproliferative activity -albeit with decreased potency -despite a groundstate dihedral angles and a steep energetic well that varies substantially from known AC dihedral angle binding. Results and Discussion.