New highly active taxoids from 9β-dihydrobaccatin-9,10-acetals. Part 2

To investigate structure–activity relationships of the 9,10-acetal-9β-dihydro taxoids, we modified the 7-hydroxyl groups of the 9,10-acetonide-3′-(4-pyridyl) analogue to deoxy, methoxy, α-F, and 7β,8β-methano group. As a result of this study, we found that the 7-deoxy analogue was the strongest among these analogues. In addition, we found that the 7-deoxy-3′-(4-pyridyl) and 7-deoxy-3′-(2-pyridyl) analogues showed stronger activity against cell lines expressing P-glycoprotein than the corresponding 3′-phenyl analogue.