Biotransformation of Glabratephrin, a Rare Type of Isoprenylated Flavonoids, by Aspergillus niger

2008 ◽  
Vol 63 (7-8) ◽  
pp. 561-564 ◽  
Author(s):  
Abou-El-Hamd H Mohamed ◽  
Ali K. Khalafallah ◽  
Afifi H. Yousof
Keyword(s):  
Aspergillus Niger ◽  
Ring Opening ◽  
Microbial Transformation ◽  
Membered Ring ◽  
Nmr Studies ◽  
Rare Type ◽  
Tephrosia Purpurea ◽  
Isolated Compound

Microbial transformation of glabratephrin, the major isolated compound from Tephrosia purpurea, afforded pseudosemiglabrin. The formation of the transformed compound seems to be performed via ring opening-closure of a five-membered ring causing transformation from a spiro into a fused system. The structure of the transformed compound was determined by comprehensive NMR studies, including DEPT, COSY, HMQC, NOE and MS.

scholarly journals A Novel Antimicrobial Phenanthrene Alkaloid from Bryopyllum pinnatum

2011 ◽  
Vol 8 (3) ◽  
pp. 1456-1461 ◽  
Author(s):  
Donatus Ebere Okwu ◽  
Fred Uchenna Nnamdi
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Candida Albicans ◽  
Aspergillus Niger ◽  
Ethanolic Extract ◽  
Klebsiella Pneumonia ◽  
Antimicrobial Studies ◽  
Prevention And Treatment ◽  
Kalanchoe Pinnata ◽  
Isolated Compound

Phenenthrene alkaloid identified as 1-ethanamino 7 hex-1-yne-5I-one phenanthrene was isolated from the ethanolic extract of the leaves ofBryophyllum pinnatum(syn. B. calcinum kalanchoe pinnata) a versatile Nigeria medicinal plant. The structure was elucidated using NMR, IR, UV and MS spectral data. Antimicrobial studies showed that the isolated compound successfully inhibitedPsuedomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus, Escherichia coli, Candida albicansandAspergillus niger. This result authenticates the use ofbryophyllum pinantumin phytomedicine for disease prevention and treatment of infections.

Delineating the possibilities for intramolecular interception of the squarate ester cascade through the use of metalated enecarbamates

2000 ◽  
Vol 78 (6) ◽  
pp. 689-696 ◽  
Author(s):  
Jinsung Tae ◽  
Leo A Paquette
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Sequential Treatment ◽  
Nucleophilic Attack ◽  
Ring Strain ◽  
Multistep Process

Highly functionalized and annulated 2,4-cyclooctadienones are formed in a stereoselective manner by sequential treatment of squarate esters with a lithiated enecarbamate (six-membered ring or larger) and a cycloalkenyl- or 1-alkenyllithium reagent. The mechanistic details of this multistep process are presented. Particular attention is drawn to the step that involves intramolecular nucleophilic attack by a proximal oxido anion at the carbamate carbonyl and results in redirection of the cascade. This step is thwarted when five-membered cyclic enecarbamates are employed because of the excessive buildup of ring strain in the associated transition state.Key words: squarate esters, enecarbamates, conrotatory ring opening, intramolecular acylation, alkenyllithium reagents.

scholarly journals Silylated gallium and indium chalcogenide ring systems as potential precursors to ME (E=O, S) materials

2013 ◽  
Vol 11 (7) ◽  
pp. 1225-1238
Author(s):  
Iliana Medina-Ramírez ◽  
Cynthia Floyd ◽  
Joel Mague ◽  
Mark Fink
Keyword(s):  
Thermal Decomposition ◽  
Room Temperature ◽  
Membered Ring ◽  
Molecular Structures ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
High Yields ◽  
Vt Nmr ◽  
State 1

AbstractThe reaction of R3M (M=Ga, In) with HESiR′3 (E=O, S; R′3=Ph3, iPr3, Et3, tBuMe2) leads to the formation of (Me2GaOSiPh3)2(1); (Me2GaOSitBuMe2)2(2); (Me2GaOSiEt3)2(3); (Me2InOSiPh3)2(4); (Me2InOSitBuMe2)2(5); (Me2InOSiEt3)2(6); (Me2GaSSiPh3)2(7); (Et2GaSSiPh3)2(8); (Me2GaSSiiPr3)2(9); (Et2GaSSiiPr3)2(10); (Me2InSSiPh3)3(11); (Me2InSSiiPr3)n(12), in high yields at room temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state, (1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M2E2 four-membered ring. VT-NMR studies of (7) show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)–(12) was examined by TGA and range from 200 to 350°C. Bulk pyrolysis of (1) and (2) led to the formation of Ga2O3; (4) and (5) In metal; (7)–(10) GaS and (11)–(12) InS powders, respectively.

ChemInform Abstract: Five- and Six-Membered Ring Opening of Pyroglutamic Diketopiperazine.

ChemInform ◽  
2010 ◽  
Vol 33 (34) ◽  
pp. no-no
Author(s):  
Dennis A. Parrish ◽  
Lon J. Mathias
Keyword(s):  
Ring Opening ◽  
Membered Ring

Diyne Cyclization in Camphor Derivatives - Experimental and Theoretical Investigation

1996 ◽  
Vol 51 (11) ◽  
pp. 1655-1662 ◽  
Author(s):  
Gabriele Wagner ◽  
Christian Heiß ◽  
Uwe Verfiirth ◽  
Rudolf Herrmann
Keyword(s):  
Oxygen Atom ◽  
Theoretical Investigation ◽  
Positive Charge ◽  
Membered Ring ◽  
Titanium Chloride ◽  
Nmr Studies ◽  
Methylene Carbon ◽  
Camphor Derivatives ◽  
Exocyclic Methylene ◽  
Derivatives Of

Derivatives of 3-oxo-camphorsulfonimide (1) with two phenylethynyl groups in the endo positions at the carbons C-2 and C-3 were prepared, and their reactivity towards halogenes and titanium chloride was studied. In every case, the two ethynyl groups led to the annulation of a five-membered ring to the bicyclo[2 .2 .1] system in an orientation which depends on the bulkiness of the additional substituent in position 3. NMR studies show that cationic species like 6 and 8 are the first detectable intermediates. They not only contain the fused five-membered ring but also a bond between its exocyclic methylene carbon and an oxygen atom of the sulfonyl group, thus transferring the positive charge mainly to sulfur. Semiempirical calculations (PM3) suggest two intermediates in the formation of such cations.

Unravelling the Mechanism and Selectivity of the NHC‐catalyzed Three‐Membered Ring‐Opening/Fluorination of Epoxy Enals: A DFT Study

ChemCatChem ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2919-2925 ◽  
Author(s):  
Yang Wang ◽  
Ling‐Bo Qu ◽  
Yu Lan ◽  
Donghui Wei
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Dft Study

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

An Unexpected Synthesis of Novel Oxygen-Bridged 1,5-Benzothiazepine Derivatives and their Reductive Five-Membered-Ring Opening

2000 ◽  
Vol 131 (4) ◽  
pp. 0393-0400 ◽  
Author(s):  
Roshan Ahmad ◽  
Mohammad Zia-ul-Haq ◽  
Shahid Hameed ◽  
Humaira Akhtar ◽  
Helmut Duddeck
Keyword(s):  
Ring Opening ◽  
Membered Ring
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