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[摘要]：Treatment of the ketoacid derivative (5) of the bioactive natural dimeric phthalide tokinolide B under weakly basic conditions and pressure, produced the novel ketal compound 6 via addition of the carboxylate of 5 to the ketone, followed by Michael addition of the alcoholate (O-alkylation) and equilibration. On the other hand, treatment of 5 with strong base (NaOH, THF, MeOH) promoted C-alkylation, affording cyclotokinolide B (7). Relative theoretical energies indicated that derivatives 6 and 7 are energetically more stable than the starting material 5. The cytotoxicities of the natural product 3 and its analogues 5-7 against selected human cancer cells are reported. |
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