Synthesis, biological activity and tubulin binding poses of 1-deoxy-9-(R)-dihydrotaxane analogs.

1-Deoxy-9alpha-dihydrotaxane analogs 9 and 10 were semi-synthesized from 1-deoxybaccatin VI, isolated from Taxus mairei, and tested for cytotoxic activity. Taxane 9 is 10-fold less cytotoxic than paclitaxel, while 10 is equally active. In the tubulin polymerization assay (ED(50) values), 10 is 4-fold less effective than paclitaxel, but 3-fold superior to 9. These observations can be explained by analysis of the corresponding taxane/beta-tubulin complexes.