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Updated: Apr 16, 2026

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
Published on: June 13, 2022
Dicarabrones A and B, a pair of new epimers dimerized from sesquiterpene lactones via a [3 + 2] cycloaddition from
Jiewei Wu, Chunping Tang, Lan Chen
1§Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, Henan 450001, China.
Abstract:
Dicarabrones A and B, a pair of epimers possessing a new skeleton featuring a cyclopentane ring connecting two sesquiterpene lactone units, were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established on the basis of spectroscopic data and were further confirmed by single-crystal X-ray crystallography. They were presumably biosynthesized from two sesquiterpenoid monomers through a [3 + 2] cycloaddition. Dicarabrones A and B showed moderate effects on HL-60 cells with IC50 values of 9.1 and 8.2 μM, respectively.
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Structure of Conjugated Dienes
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the...

