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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.
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Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom,...
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Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
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The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
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Polycycloiridals with a Cyclopentane Ring from Iris tectorum.

Chun-Lei Zhang1,2, Zhi-You Hao1, Yan-Fei Liu1

  • 1State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing 100050, People's Republic of China.

Journal of Natural Products
|December 30, 2016
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Summary
This summary is machine-generated.

Six novel iridal-type triterpenoids were discovered in Iris tectorum, with one compound showing potential anti-inflammatory properties by suppressing nitric oxide production in cell models.

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Area of Science:

  • Natural Products Chemistry
  • Organic Chemistry
  • Pharmacology

Background:

  • Iris tectorum is a plant source of bioactive compounds.
  • Triterpenoids are a diverse class of natural products with various biological activities.
  • Understanding the chemical diversity and bioactivity of plant-derived compounds is crucial for drug discovery.

Purpose of the Study:

  • To isolate and characterize novel iridal-type triterpenoids from Iris tectorum.
  • To investigate the potential anti-inflammatory activity of isolated compounds.

Main Methods:

  • Large-scale re-extraction of Iris tectorum.
  • Isolation and structure elucidation of compounds using spectroscopic methods (e.g., NMR, MS).
  • X-ray diffraction analysis for definitive structural determination.
  • In vitro assay to measure nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV2 cells.

Main Results:

  • Six new iridal-type triterpenoids, named polycycloiridals E-J (1-6), were isolated.
  • These compounds possess a unique cyclopentane ring structure.
  • The known compound spirioiridotectal D (7) was also isolated and its structure confirmed by X-ray diffraction.
  • Compound 7 exhibited significant suppression of LPS-induced NO production with an IC50 value of 0.54 μM.

Conclusions:

  • The study expands the known chemical diversity of iridal-type triterpenoids.
  • A potential biosynthesis pathway for these novel compounds was proposed.
  • Spirioiridotectal D demonstrates notable anti-inflammatory potential, warranting further investigation.