It was shown that a new taxane analogue 3, which exhibited both in vitro antitumor activity and in vivo efficacy by both iv and po administration, was prone to be metabolized by human liver microsomes. We identified a major metabolite, M-1, generated by human liver microsomes as 20a, a hydroxylated compound at the pyridine ring of 3. To improve the metabolic stability of 3, we designed and synthesized new taxane analogues based on ...