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Content available remote Ekstaza i udręka, czyli o chemii taksolu
EN
Taxol (1), highly functionalised complex diterpenoid originally derived from the bark of Pacific yew, has received in recent decade wide attention of scientists in all fields of life sciences and chemistry, after the discovery of its strong and unique anticancer properties. Fast and spectracular career of this molecule is a subject of the present review. The Jarge scale of research on taxol is the consequence of public and commercial response to successful treatment of various cancer diseases and impossibility of solving basic technological and intellectual problems such as: production, drug formulation, structure-activity relationship elucidation. The discussion is divided into following sections: 1. Activity and pharmacological phenomena of taxol. 2. Production of taxol by biotechnological and chemical methods, including synthesis of taxol side chain. 3. Structure-activity relationship (SAR) of taxoids. After Horwitz reported in 1979 a strongly antimitotic activity of taxol, interest in developing the pharmacology and biochemistry of this class of natural products increased. Taxol molecule promotes anticancer activity by enhancing polymerization of tubulin and stabilization of microtubules. This process has the effect of inhibiting the normal dynamic reorganization of the cytoskeleton (with consists of microtubules) that is necessary for interphase and cell division in mitosis. Taxol and taxotere are successfully used for the treatment of a variety of cancers, in particular ovarian and breast cancer. The biggest problem hindering wider application of this drug is its limited availability from natural sources. One kg of Taxus brevifolia bark yields only 100-170 mg of taxol, after long and complicated extraction procedure. Since the yew is slow growing species this method of obtaining the drug is controvertible and unprofitable. An alternative source of taxol is semisynthesis, where natural precursor of taxol 10-deacetylbaccatin (10-DAB) can be extracted from regenerable twigs of popular yew Taxus baccata and after coupling with synthetically prepared side chain can be converted to taxol or taxotere. Taxol has also been prepared by a number of total syntheses but none of these is expected to enter the phase of commercial production. Biotechnological approaches to production by tissue culture or fungi cultivation have been reprted. Studies in the area of taxoids structure-activity relationships have first demonstrated two basic principles. The so-called 'southern' substituents, such as C-2 benzoate and the side chain, are crucial for the activity. 'Northern' substituents at C-7, C-9 and C-10 can be changed without drastic effect on the activity. The role of the substituents at C-1, the oxetane ring and diterpenoid core modifications are less well understood. There are many reports of significant activity of highly transformed taxoids, including those with: modified ABC core, open C-ring structure and aromatic C-ring. These results indicate the possibility of obtaining a synthetic, structurally simplified variant of taxol.
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