1. Granatripodins A-B, limonoids featuring a Tricyclo[3.3.1.02,8]nonane motif: Absolute configuration and agonistic effects on human pregnane-X-receptor
Li Shen, Xiao-Peng Zou, Wan-Shan Li, Attila Mándi, Tibor Kurtán, Jun Wu Bioorg Chem. 2021 Jun;111:104888. doi: 10.1016/j.bioorg.2021.104888. Epub 2021 Apr 5.
Two unprecedented limonoids incorporating a sterically encumbered cyclopropane ring, named granatripodins A (1) and B (2), featuring the presence of a tricyclo[3.3.1.02,8]nonane motif, were obtained from seeds of the Thai Xylocarpus granatum. The planar structures and absolute configurations of these limonoids were unambiguously established by NMR investigations, TDDFT-ECD and DFT-NMR calculations, and single-crystal X-ray diffraction analysis (Cu Kα). Most notably, granatripodin A (1) exhibited agonistic effects on human pregnane-X-receptor at the concentration of 100.0 nM. The biosynthetic origins of these limonoids via a radical cascade reaction are proposed. This study exemplifies a universal approach for the stereochemical assignment of polycyclic compounds with a cyclopropane-embedded cage scaffold.
2. Callintegers A and B, Unusual Tricyclo[4.4.0.09,10]tetradecane Clerodane Diterpenoids from Callicarpa integerrima with Inhibitory Effects on NLRP3 Inflammasome Activation
De-Wen Bi, Feng Xiong, Bin Cheng, Ya-Ling Zhou, Muhammad Aurang Zeb, Peng Tang, Wen-Hui Pang, Rui-Han Zhang, Xiao-Li Li, Xing-Jie Zhang, Wei-Lie Xiao J Nat Prod. 2022 Nov 25;85(11):2675-2681. doi: 10.1021/acs.jnatprod.2c00568. Epub 2022 Oct 26.
Callintegers A (1) and B (2), unprecedented clerodane norditerpenoids based on a novel carbon skeleton, were isolated from Callicarpa integerrima. Compounds 1 and 2 possess a novel 6/6/6-fused tricyclic ring system. Their structures and absolute configurations were determined by quantum chemical calculations, spectroscopic analysis, and single-crystal X-ray diffraction methods. Biological evaluation showed that compound 2 inhibited IL-1β secretion in a dose-dependent manner with an IC50 value of 5.5 ± 3.2 μM. Caspase-1 maturation and IL-1β secretion were also reduced, indicating that compound 2 impaired NLRP3 inflammasome activation.
3. Incarnolides A and B, Two Schinortriterpenoids with a Tricyclo[9.2.1.02,8]tetradecane-Bridged System from Schisandra incarnata
Juan Chen, Xiao-Gang Peng, Junjun Liu, Ying Gao, Ming Zhou, Jia Zhou, Jian Song, Han-Li Ruan Org Lett. 2020 Feb 7;22(3):1071-1075. doi: 10.1021/acs.orglett.9b04600. Epub 2020 Jan 15.
Incarnolides A (1) and B (2), two schinortriterpenoids (SNTs) featuring a tricyclo[9.2.1.02,8]tetradecane-bridged system, together with two biosynthetically related known SNTs, lancifonins A (3) and C (4), were isolated from the stems of Schisandra incarnata. Their structures were elucidated by extensive spectroscopic analyses, and the absolute configurations were assigned by single-crystal X-ray diffraction and electronic circular dichroism calculation. The hypothetical biogenetic pathway of 1 and 2 was postulated. Compound 1 exhibited antiviral and neuroprotective activities.
