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Related Concept Videos

Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

4.2K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
4.2K
Conformations of Cycloalkanes02:29

Conformations of Cycloalkanes

16.3K
Adolf von Baeyer attempted to explain the instabilities of small and large cycloalkane rings using the concept of angle strain — the strain caused by the deviation of bond angles from the ideal 109.5° tetrahedral value for sp3  hybridized carbons. However, while cyclopropane and cyclobutane are strained, as expected from their highly compressed bond angles, cyclopentane is more strained than predicted, and cyclohexane is virtually strain-free. Hence, Baeyer’s theory that...
16.3K
Chair Conformation of Cyclohexane02:02

Chair Conformation of Cyclohexane

21.0K
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
21.0K
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

14.7K
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?  
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n +...
14.7K
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

4.2K
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
4.2K
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

4.3K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
4.3K

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Transient Expression in Nicotiana Benthamiana Leaves for Triterpene Production at a Preparative Scale
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Cycloartane triterpenes from Beesia calthaefolia and their anticomplement structure-activity relationship study.

Li-Hua Mu1, Jin-Yuan Zhao1, Jing Zhang2

  • 1a Department of Clinical Pharmacology , General Hospital of PLA , Beijing 100853 , China.

Journal of Asian Natural Products Research
|May 4, 2016
PubMed
Summary

This study identified a new cycloartane triterpenoid from Beesia calthaefolia and explored structure-activity relationships for anticomplement activity. Specific hydroxyl group configurations and glycosyl substitutions significantly impact this activity.

Keywords:
Beesia calthaefoliaanticomplement activitycycloartane glycosidestructure–activity relationship

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Area of Science:

  • Natural Products Chemistry
  • Immunology
  • Pharmacology

Background:

  • Beesia calthaefolia is a source of cycloartane triterpenes.
  • Triterpenes possess diverse biological activities, including immunomodulatory effects.
  • The complement system plays a crucial role in innate immunity.

Purpose of the Study:

  • To isolate and characterize cycloartane triterpenoids from Beesia calthaefolia.
  • To evaluate the anticomplement activity of isolated compounds via the classic pathway.
  • To investigate the structure-activity relationships (SAR) of these compounds concerning anticomplement potency.

Main Methods:

  • Isolation of compounds using chromatographic techniques.
  • Structure elucidation via spectroscopic analyses (NMR, MS) and chemical methods.
  • Assay of anticomplement activity using the classic pathway.

Main Results:

  • Fifteen cycloartane triterpenes were isolated, including one novel compound.
  • Structure-activity relationship analysis revealed key findings: 12-α-OH is preferred over 12-β-OH; 18-OH decreases activity, while 15-OH increases it.
  • Saponins with both 15-OH and 18-OH showed reduced activity.
  • Glycosyl moiety variations (xylosyl, glucosyl, galactosyl) influenced anticomplement activity, with galactosyl showing increased potency.

Conclusions:

  • The study identified a new cycloartane triterpenoid and elucidated SAR for anticomplement activity.
  • Specific structural features, including hydroxyl group configuration and glycosyl type, are critical for modulating anticomplement effects.
  • Further SAR studies are warranted to understand the impact of additional functionalizations on anticomplement saponins.