| Autor: |
Bai, R., Bates, R. B., Hamel, E., Moore, R. E., Nakkiew, P., Pettit, G. R., Sufi, B. A. |
| Zdroj: |
Journal of Natural Products; December 2002, Vol. 65 Issue: 12 p1824-1829, 6p |
| Abstrakt: |
The synthesis of a lyngbyastatin 1−Ibu-epilyngbyastatin 1 mixture combined with NMR and molecular modeling studies proved that natural lyngbyastatin 1 was only one Ibu epimer rather than a mixture of both and that the configuration of this epimer in the Ibu unit was R. The substance isolated with lyngbyastatin 1 was Ibu-epidolastatin 12. The extreme broadness in the proton NMR spectra of lyngbyastatin 1 and Ibu-epidolastatin 12 was exchange broadening due to rotation about the Ibu−Ala amide bond. It was a consequence of (1) a small energy difference between the cis and trans forms of this bond, (2) a substantial difference in conformation between these forms, and (3) a lowered barrier between them compared to most amide bonds (due to steric hindrance). The synthetic lyngbyastatin 1−Ibu-epilyngbyastatin 1 mixture had significant activities against cancer cells and in stimulating actin polymerization, but was less active than dolastatin 11 in all assays. |
| Databáze: |
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