scholarly journals Synthesis of fused tricyclic amines unsubstituted at the ring-junction positions by a cascade condensation, cyclization, cycloaddition then decarbonylation strategy

2012 ◽  
Vol 8 ◽  
pp. 107-111 ◽  
Author(s):  
Iain Coldham ◽  
Adam J M Burrell ◽  
Hélène D S Guerrand ◽  
Luke Watson ◽  
Nathaniel G Martin ◽  
...  
Keyword(s):  
Ring System ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Reaction Sequence ◽  
Hydroxymethyl Group ◽  
The Core ◽  
Stereochemical Control ◽  
Ring Junction ◽  
Group A ◽  
Very High

Heating aldehydes that contain a protected hydroxymethyl group, a tethered alkyl chloride and a tethered alkenyl group at the α-position of the aldehyde with an amine sets up a cascade (tandem) reaction sequence involving condensation to an intermediate imine, then cyclization and formation of an intermediate azomethine ylide and then intramolecular dipolar cycloaddition. The fused tricyclic products are formed with complete or very high stereochemical control. The hydroxymethyl group was converted into an aldehyde – which could be removed to give the tricyclic amine products that are unsubstituted at the ring junction positions – or was converted into an alkene, which allowed the formation of the core ring system of the alkaloids scandine and meloscine.

Transannular dipolar cycloaddition as an approach towards the synthesis of the core ring system of the sarain alkaloids

2011 ◽  
Vol 9 (6) ◽  
pp. 1901 ◽  
Author(s):  
Andrew I. Franklin ◽  
David Bensa ◽  
Harry Adams ◽  
Iain Coldham
Keyword(s):  
Ring System ◽  
Dipolar Cycloaddition ◽  
The Core

Stereoselective construction of 5,11-methanomorphanthridine and 5,10b-phenanthridine structural frameworks: Total syntheses of (±)-pancracine, (±)-brunsvigine, (±)-maritidine, and (±)-crinine

2012 ◽  
Vol 84 (7) ◽  
pp. 1597-1619 ◽  
Author(s):  
Ganesh Pandey ◽  
Smita R. Gadre
Keyword(s):  
Total Synthesis ◽  
Core Structure ◽  
Biologically Active ◽  
Single Electron ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Total Syntheses ◽  
The Core ◽  
One Step

The core structure of the complex pentacyclic 5,11-methanomorphanthridine skeleton and the vicinal quaternary and tertiary stereocenters of the 5,10b-phenanthridine skeleton are constructed stereospecifically in one step employing intramolecular 1,3-dipolar cycloaddition of a nonstabilized azomethine ylide (AMY) generated by the sequential double desilylation of appropriate bis-trimethylsilylmethyl amines using Ag(I)F as a single-electron oxidant. The strategy is successfully applied for the total synthesis of biologically active alkaloids such as (±)-pancracine, (±)-brunsvigine, (±)-maritidine, and (±)-crinine.

scholarly journals Synthesis of the tricyclic core of manzamine A

2015 ◽  
Vol 13 (11) ◽  
pp. 3331-3340 ◽  
Author(s):  
Ravindra B. Pathak ◽  
Benjamin C. Dobson ◽  
Nandita Ghosh ◽  
Khalid A. Ageel ◽  
Madeha R. Alshawish ◽  
...  
Keyword(s):  
Ring System ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Manzamine A ◽  
Tricyclic Core ◽  
Manzamine Alkaloids

An approach to the ABC tricyclic ring system of the manzamine alkaloids has been achieved. A key step is the intramolecular dipolar cycloaddition of an azomethine ylide.

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

Reactions of 4-Pyrones with Azomethine Ylides as a Chemo­selective Method for the Construction of Multisubstituted Pyrano[2,3-c]pyrrolidines

Synthesis ◽  
2021 ◽  
Author(s):  
Dmitrii L. Obydennov ◽  
Vyacheslav D. Steben’kov ◽  
Konstantin L. Obydennov ◽  
Sergey A. Usachev ◽  
Vladimir S. Moshkin ◽  
...  
Keyword(s):  
Double Bond ◽  
Ring Opening ◽  
Azomethine Ylides ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Computational Studies ◽  
Carbon Double Bond ◽  
Reactivity Indexes ◽  
Reaction Proceeds

Abstract4-Pyrones bearing electron-donating and electron-withdrawing groups react with nonstabilized azomethine ylides to form pyrano[2,3-c]pyrrolidines in moderate to good yields. The reaction proceeds chemoselectively as a 1,3-dipolar cycloaddition of the azomethine ylide at the carbon–carbon double bond of the pyrone activated by the electron-withdrawing substituent. The reactivity of 4-pyrones toward azomethine ylides was rationalized by computational studies with the use of reactivity indexes. The pyrano[2,3-c]pyrrolidine moiety could be modified, for example by a ring-opening transformation under the action of hydrazine to provide pyrazolyl-substituted pyrrolidines.

scholarly journals Studies on the Enantioselective Synthesis of E-Ethylidene-bearing Spiro[indolizidine-1,3′-oxindole] Alkaloids

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 428
Author(s):  
Nihan Yayik ◽  
Maria Pérez ◽  
Elies Molins ◽  
Joan Bosch ◽  
Mercedes Amat
Keyword(s):  
Ring System ◽  
Enantioselective Synthesis ◽  
Synthetic Route ◽  
Hydroxymethyl Group ◽  
Hydride Reduction ◽  
Lactam Carbonyl ◽  
Key Steps ◽  
Oxindole Alkaloids

A synthetic route for the enantioselective construction of the tetracyclic spiro[indolizidine-1,3′-oxindole] framework present in a large number of oxindole alkaloids, with a cis H-3/H-15 stereochemistry, a functionalized two-carbon substituent at C-15, and an E-ethylidene substituent at C-20, is reported. The key steps of the synthesis are the generation of the tetracyclic spirooxindole ring system by stereoselective spirocyclization from a tryptophanol-derived oxazolopiperidone lactam, the removal of the hydroxymethyl group, and the stereoselective introduction of the E-ethylidene substituent by acetylation at the α-position of the lactam carbonyl, followed by hydride reduction and elimination. Following this route, the 21-oxo derivative of the enantiomer of the alkaloid 7(S)-geissoschizol oxindole has been prepared.

Heterogeneity in epidemic models and its effect on the spread of infection

1998 ◽  
Vol 35 (3) ◽  
pp. 651-661 ◽  
Author(s):  
Håkan Andersson ◽  
Tom Britton
Keyword(s):  
Heterogeneous Population ◽  
Epidemic Models ◽  
Homogeneous Population ◽  
Epidemic Size ◽  
Infection Pressure ◽  
Group A ◽  
Final Epidemic Size ◽  
Spread Of Infection ◽  
Very High ◽  
High Infectivity

We first study an epidemic amongst a population consisting of individuals with the same infectivity but with varying susceptibilities to the disease. The asymptotic final epidemic size is compared with the corresponding size for a homogeneous population. Then we group a heterogeneous population into households, assuming very high infectivity within households, and investigate how the global infection pressure is affected by rearranging individuals between the households. In both situations considered, it turns out that whether or not homogenizing the individuals or households will result in an increased spread of infection actually depends on the infectiousness of the disease.

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