Synthetic Reactions with Rare Taccalonolides Reveal the Value of C-22,23 Epoxidation for Microtubule Stabilizing Potency

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• 作者：Jiangnan Peng ; April L. Risinger ; Jing Li ; Susan L. Mooberry
• 刊名：Journal of Medicinal Chemistry
• 出版年：2014
• 出版时间：July 24, 2014
• 年：2014
• 卷：57
• 期：14
• 页码：6141-6149
• 全文大小：494K
• ISSN：1520-4804

文摘

The taccalonolides are microtubule stabilizers isolated from plants of the genus Tacca. Taccalonolide AF is 231 times more potent than the major metabolite taccalonolide A and differs only by the oxidation of the C-22,23 double bond in A to an epoxy group in AF. In the current study, 10 other rare natural taccalonolides were epoxidized and in each case epoxidation improved potency. The epoxidation products of taccalonolide T and AI were the most potent, with IC₅₀ values of 0.43 and 0.88 nM, respectively. These potent taccalonolides retained microtubule stabilizing effects, and T-epoxide demonstrated antitumor effects in a xenograft model of breast cancer. Additional reactions demonstrated that reduction of the C-6 ketone resulted in an inactive taccalonolide and that C-22,23 epoxidation restored its activity. These studies confirm the value of C-22,23 epoxidation as an effective strategy for increasing the potency of a wide range of structurally diverse taccalonolide microtubule stabilizers.