Spiroketals of Pestalotiopsis fici Provide Evidence for a Biosynthetic Hypothesis Involving Diversified Diels鈥揂lder Reaction Cascades

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• 作者：Ling Liu ; Yan Li ; Li Li ; Ya Cao ; Liangdong Guo ; Gang Liu ; Yongsheng Che
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：April 5, 2013
• 年：2013
• 卷：78
• 期：7
• 页码：2992-3000
• 全文大小：448K
• 年卷期：v.78,no.7(April 5, 2013)
• ISSN：1520-6904

文摘

Chloropestolides B鈥揋 (1鈥?b>6), six new metabolites featuring the chlorinated spiro[benzo[d][1,3]dioxine-2,7鈥?bicyclo[2.2.2]octane]-4,8鈥?dione (1鈥?b>3) and spiro[benzo[d][1,3]dioxine-2,1鈥?naphthalene]-2鈥?4-dione (4鈥?b>6) skeletons, and their putative biosynthetic precursor dechloromaldoxin (7) were isolated from the scale-up fermentation cultures of the plant endophytic fungus Pestalotiopsis fici. The structures of 1鈥?b>7 were determined mainly by NMR experiments. The absolute configurations of 1鈥?b>3 were deduced by analogy to the previously isolated metabolites from the same fungus (9 and 13鈥?b>18), whereas those of 4, 5, and 7 were assigned by electronic circular dichroism (ECD) calculations. Structurally, the spiroketal skeletons found in 1鈥?b>3 and 4鈥?b>6 could be derived from 2,6-dihydroxy-4-methylbenzoic acid with chlorinated bicyclo[2.2.2]oct-2-en-5-one and 4a,5,8,8a-tetrahydronaphthalen-2(1H)-one, respectively. Biogenetically, compounds 1鈥?b>6 were derived from the same Diels鈥揂lder precursors as the previously isolated 9 and 12鈥?b>18. In addition, compounds 2 and 3 were proposed as the biosynthetic intermediates of 17 and 16, respectively. Compound 1 was cytotoxic to three human tumor cell lines.