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RISS 인기검색어
- 검색키워드
- 저자 : FU PENG (검색결과 2 건)
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PENG, LEE FU HARVARD UNIVERSITY 1999 해외박사(DDOD)
The first total synthesis of fumonisin B<sub>2</sub> (FB<sub>2</sub>, <bold> 1</bold>) was accomplished in a stereoselective and enantioselective manner from the building blocks <bold>23</bold>, <bold>24</bold>, and <bold>25</bold>. The key steps included: (1) an iodolactonization/double inversion sequence to stereoselectively introduce the C14 and C15 hydroxyl groups, (2) two consecutive reagent-controlled asymmetric allylations to stereoselectively set the C3 and C5 hydroxyl moieties, and (3) a reagent-controlled asymmetric Michael addition to enantioselectively introduce the stereocenter of fragment <bold> 25</bold>. The convergent nature of the synthesis and the flexibility of the preparation of the fragments permitted the facile synthesis of several analogs of FB<sub>2</sub>.*. Both cytotoxicity assays and ceramide synthase inhibition assays were used to evaluate the biological activity of the fumonisin analogs. Our findings indicated that fumonisin-mediated cytotoxicity was not substrate specific and was not influenced by the stereochemistry of the analogs. Such cytotoxicity, therefore, occurred via several different mechanisms and was effected through a variety of receptors. The ceramide synthase inhibition assays determined that the minimum structural requirements for the maximum amount of enzymatic inhibition consisted of negatively charged carboxylic residues connected to a long alkyl chain. The laxity of these binding requirements accounted for the low substrate specificity of ceramide synthase and the discovery that enzymatic inhibition was not influenced by the stereochemistry of the analogs. Furthermore, those analogs which contained only the aforementioned minimal structural elements were equally active and were the most potent compounds that were examined. More interestingly, the set of minimal structural requirements for inhibition exhibited some structural correlations with coenzyme A, with the carboxylic acid groups mimicking the phosphate groups and the long alkyl chain substituting for the backbone. Thus, in the new revised model of ceramide synthase inhibition by fumonisins, the fumonisins act by mimicking coenzyme A, shutting down the enzyme by binding to and blocking its coenzyme A binding site.*. *Please refer to dissertation for diagrams.
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