The absolute configurations of hyperilongenols A-C: rare 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinols with enolizable β,β′-tricarbonyl systems from Hypericum longistylum Oliv.
The absolute configurations of hyperilongenols A-C: rare 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinols with enolizable β,β′-tricarbonyl systems from Hypericum longistylum Oliv.
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DOI：
10.1039/c9qo00245f
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发表时间：
2019-05-07
影响因子：
5.4
通讯作者：
Zhang, Yonghui
中科院分区：
文献类型：
--
作者：
Zhang, Na;Shi, Zhengyi;Zhang, Yonghui
从金丝桃茎叶中分离得到3个新的12，13-二环多环多戊烯基间苯三酚(PPAP)衍生物，命名为高香酚A-C(1-3)。它们的平面结构由一维和二维核磁共振、HRESIMS数据和化学衍生化相结合确定。用电子圆二色谱(ECD)和X射线结晶学确定了它们的绝对构型。化合物1-3代表了自然产生的12，13-二螺环PPAP的第一个例子，该PPAP具有可烯醇化的β，β‘-三甲酰基体系。化合物1-3的O-甲基化，结合对其在不同溶剂中的X-射线衍射数据和变温1H核磁共振谱的综合分析，使我们能够提出形成高香草酚A(1)不可分离的C-24同分异构体的一般机理，破译溶剂对可烯化的β，β‘-三羰基烯醇质子的影响，并探索化合物1-3的酮-烯醇相互转化的可能性。此外，还提出了具有可烯化的β-二羰基和β，β‘-三羰基体系的PPAP结构测定的合理建议。此外，体外生物活性测定表明，化合物2对金黄色葡萄球菌具有较强的抗菌活性。
Three novel 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinol (PPAP) derivatives, named hyperilongenols A-C (1-3), were isolated from the stems and leaves of Hypericum longistylum Oliv. Their planar structures were established by a combination of 1D and 2D NMR, HRESIMS data, and chemical derivatization. Their absolute configurations were defined using electronic circular dichroism (ECD) spectroscopy and X-ray crystallography. Compounds 1-3 represent the first examples of naturally occurring 12,13-seco-spirocyclic PPAPs with an enolizable beta, beta'-tricarbonyl system. The O-methylation of compounds 1-3, coupled with comprehensive analyses of their X-ray diffraction data and variable-temperature 1H NMR spectra collected in different solvents, allowed us to propose a general mechanism underlying the formation of inseparable C-24 epimers of hyperilongenol A (1), decipher the solvent effects on the enolizable beta, beta'-tricarbonyl enol protons, and explore the possibilities of keto-enol interconversions of compounds 1-3. Moreover, a reasonable proposal for the structural determination of PPAPs with enolizable beta-dicarbonyl and beta, beta'-tricarbonyl systems was developed. In addition, an in vitro bioassay showed that 2 exhibited potent antibacterial activity against Staphylococcus aureus.