Trigonostemons G and H,dinorditerpenoid dimers with axially chiral biaryl linkage from Trigonostemon chinensis |
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Authors: | Qin Zhu Chunping Tang Attila Mándi Tibor Kurtán Yang Ye |
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Institution: | 1. State Key Laboratory of Drug Research and Department of Natural Products Chemistry, Shanghai Institute of Materia Medica Chinese Academy of Sciences, Shanghai, PR China;2. Department of Organic Chemistry, University of Debrecen, Debrecen, Hungary |
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Abstract: | Trigonostemons G and H, two novel dimeric dinorditerpenoids, were isolated from the stem barks of Trigonostemon chinensis. Their planar structures and relative configurations were established by extensive analysis of spectroscopic data. Trigonostemons G and H possess a homodimeric biaryl skeleton obtained from two rearranged chiral nonracemic abietane-type dinorditerpenes through an axially chiral biaryl 11,11′-linkage. Torsional scan and computation of the transition states were carried out to estimate the rotational energy barrier, and the axial chirality (aS) was determined by time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The positive n-π* ECD transitions of the isolated carbonyl chromophore above 300 nm could be used to determine the central chirality of trigonostemon G independently by ECD calculations of the diastereomers. |
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Keywords: | axial and central chirality dimeric dinorditerpenoid Trigonostemon chinensis trigonostemon G trigonostemon H TDDFT-ECD |
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