Atropisomeric meroterpenoids with rare triketone-phloroglucinol-terpene hybrids from Baeckea frutescens.
Atropisomeric meroterpenoids with rare triketone-phloroglucinol-terpene hybrids from Baeckea frutescens.
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DOI：
10.1039/c8ob02433b
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发表时间：
2018-11
影响因子：
3.2
通讯作者：
Jiqin Hou;Bao-Lin Wang;Chao Han;Jian Xu;Zhe Wang;Qingguo He;Pei-Lin Zhang;Shumei Zhao;Xinmiao Pei;Hao Wang
中科院分区：
文献类型：
--
作者：
Jiqin Hou;Bao-Lin Wang;Chao Han;Jian Xu;Zhe Wang;Qingguo He;Pei-Lin Zhang;Shumei Zhao;Xinmiao Pei;Hao Wang
Baefrutones A-F (1-6) 是六种具有稀有三酮-间苯三酚-单萜/倍半萜骨架的新间萜类化合物，及其生物合成相关中间体 (±)-baeckenon B (7)，是在 HPLC-Q/TOF-MS2 研究指导下从 Baeckea frutescens 的地上部分分离出来的。化合物 1-4 代表天然类萜的第一个例子，以四对不可分离的非对映异构体阻转异构体（2:1，1H NMR 积分）存在，这是由于 C-1 羰基和 2'-OH 之间的分子内氢键引起的 C-6-C-7-C-1' 键周围的限制旋转引起的。这些结构的发现不仅极大地丰富了类萜和阻转异构体库的化学多样性，而且对于不对称有机合成来说也可能是令人兴奋和具有挑战性的。它们的结构和绝对构型是通过广泛的光谱分析、X 射线衍射和 ECD 计算确定的。化合物5和6是由7和β-石竹烯通过区域选择性氧化杂Diels-Alder反应仿生合成的，从而为构建6/6/9/4四环系统提供了途径。还讨论了这些类萜的抗炎活性。
Baefrutones A-F (1-6), six new meroterpenoids with rare triketone-phloroglucinol-monoterpene/sesquiterpene frameworks, together with their biosynthetically related intermediate (±)-baeckenon B (7), were isolated from the aerial part of Baeckea frutescens under the guidance of HPLC-Q/TOF-MS2 investigation. Compounds 1-4 represent the first examples of natural meroterpenoids existing as four pairs of inseparable diastereomeric atropisomers (2 : 1, 1H NMR integration) caused by the restricted rotation around the C-6-C-7-C-1' bonds arising from the intramolecular hydrogen bond between C-1 carbonyl and 2'-OH. The discovery of these architectures not only largely enriched the chemodiversity of the meroterpenoid and atropisomer library, but also might be exciting and challenging for asymmetric organic synthesis. Their structures and absolute configurations were established by extensive spectroscopic analysis, X-ray diffraction, and ECD calculations. Compounds 5 and 6 were biomimetically synthesized from 7 and β-caryophyllene via a regioselective oxidative hetero-Diels-Alder reaction, thus providing access to the construction of the 6/6/9/4 tetracyclic ring system. The anti-inflammatory activities of these meroterpenoids were also discussed.