Dipolare (1:1)‐Addukte aus der Reaktion von 3‐Amino‐2<i>H</i>‐azirinen mit 1,3,4‐Oxadiazol‐ und 1,3,4‐Thiadiazol‐2(3<i>H</i>)‐onen

Ametamey, Simon M.; Vincent, Beverly R.; Heimgartner, Heinz

doi:10.1002/hlca.19900730230

Cited by 20 publications

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References 31 publications

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“…Moreover, the 13 C NMR signal of the imidothioate moiety appears at low field (194−204 ppm), due to its participation in an aza/thiaallyl anionic subunit (Scheme ). Dipolar structures similar to 10 have been described as the results of addition reactions between 3‐amino‐2 H ‐aziridines and 1,3,4‐thiadiazol‐2(3 H )‐ones 17. The isolated intermediates 10 possess an interesting property: if they are heated to slightly above their melting points they are completely transformed into the corresponding guanidines 5 through an intramolecular S N reaction.…”

Section: Resultsmentioning

confidence: 99%

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways

et al. 2003

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The formation of highly reactive zwitterionic triaziniumimidothioate intermediates 10 from bis(1,3,4-thiadiazolo)-1,3,5-triazinium halides is reported. These intermediates are the first structures to be isolated from the reaction pathway between bis(1,3,4-thiadiazolo)-1,3,5-triazinium halides 1 and benzylamines 2. The reaction between 1 and 2 has a very complicated hypersurface and can yield unusual bis(1,2,4-triazolo)-1,3,5-triazinium halides 6, [1,2,4]triazolo [1,3,4]thiadiazolo[1,3,5]triazinium halides 7 or highly substituted guanidines 5. The formation of 6 and 7 can be understood in terms of an S N (ANRORC) process. As could be demonstrated for the tricyclic cations 6, these compounds, together with 7,

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Section: Resultsmentioning

confidence: 99%

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways

et al. 2003

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3‐Amino‐2H‐azirine, Bausteine für α,α‐disubstituierte α‐Aminosäuren in Heterocyclen‐ und Peptidsynthesen

Heimgartner

1991

Angewandte Chemie

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Mit dem erneuten Aufschwung der Peptidchemie ist auch das Interesse an nicht-proteinogenen Aminosauren gestiegen. Dazu gehoren unter anderem a,a-disubstituierte Glycine, deren bekanntester Vertreter Aib (2-Aminoisobuttersaure, 2-Methylalanin) ist. Diese a-Aminosauren kommen in naturlichen Oligopeptiden vor, z.B. in den Peptaibolen, einer Klasse Membran-aktiver Ionophore, die aus Pilzkulturen gewonnen werden. Die zweifache Substitution am a-CAtom von Aminosauren schrankt die konformationelle Freiheit von Peptiden stark ein. Dadurch werden bestimmte Sekundarstrukturen begunstigt; so induzieren a,a-disubstituierte a-Aminosauren die Bildung von b-Turns oder Helices. Fur den Aufbau von Oligopeptiden, cyclischen Peptiden und Depsipeptiden (Peptoliden), die solche updisubstituierte a-Aminosauren enthalten, sind 3-Amino-2H-azirine ideate Ausgangsstoffe. Die Ringspannung dieser Molekiile ermoglicht ihren Einsatz bei Peptid-Kupplungen, ohne daR zusatzliche aktivierende Reagentien notwendig sind. Unter Venvendung von 3-Amino-2H-azirinen 1aBt sich auch eine groBe Zahl von Heterocyclen synthetisieren, die a,?-disubstituierte a-Aminosauren als Bauelemente im Geriist aufweisen. Treibende Kraft dieser Reaktionen 1st die Entspannung bei der Offnung des dreigliedrigen Ringes, die meist in einer Ringerweiterungsreaktion erfolgt. Die mechanistische Abklarung der zum Teil komplizierten Reaktionsverlaufe bietet einige Uberraschungen.

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3‐Amino‐2H‐Azirines. Synthons for α,α‐Disubstituted α‐Amino Acids in Heterocycle and Peptide Synthesis [New Analytical Methods (43)]

Heimgartner

1991

Angew. Chem. Int. Ed. Engl.

244

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The recent upswing in peptide chemistry has been accompanied by an increasing interest in nonproteinogenic amino acids. These include the α,α‐disubstituted glycines, the best known of which is Aib (2‐aminoisobutyric acid, 2‐methylalanine). These α‐amino acids occur in natural oligopeptides such as the peptaibols, a class of membrane‐active ionophores that has been isolated from fungal cultures. The twofold substitution at the α‐C atom of the amino acids severely restricts the conformational freedom of the peptides and causes particular secondary structures to be favored; thus, α, α‐disubstituted α‐amino acids induce the formation of β turns or helices. 3‐Amino‐2H‐azirines are ideal synthons for the construction of oligopeptides, cyclic peptides and depsipeptides (peptolides) containing such α,α‐disubstituted α‐amino acids. The presence of the ring strain in these molecules means that they can be used in peptide coupling without the need for additional activating reagents. Using 3‐amino‐2H‐azirines a large array of heterocycles containing α, α‐disubstituted α‐amino acids as structural elements within their skeleton can be synthesized. The driving force in these reactions is the release of the strain on the three‐membered ring, which usually takes place in a ring‐expansion reaction. The mechanistic elucidation of these reactions, which can be quite complex, contains some surprises.

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Dipolare (1:1)‐Addukte aus der Reaktion von 3‐Amino‐2H‐azirinen mit 1,3,4‐Oxadiazol‐ und 1,3,4‐Thiadiazol‐2(3H)‐onen

Cited by 20 publications

References 31 publications

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways

3‐Amino‐2H‐azirine, Bausteine für α,α‐disubstituierte α‐Aminosäuren in Heterocyclen‐ und Peptidsynthesen

3‐Amino‐2H‐Azirines. Synthons for α,α‐Disubstituted α‐Amino Acids in Heterocycle and Peptide Synthesis [New Analytical Methods (43)]

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Dipolare (1:1)‐Addukte aus der Reaktion von 3‐Amino‐2H‐azirinen mit 1,3,4‐Oxadiazol‐ und 1,3,4‐Thiadiazol‐2(3H)‐onen

Cited by 20 publications

References 31 publications

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel SN(ANRORC) Reaction Pathways

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel SN(ANRORC) Reaction Pathways

3‐Amino‐2H‐azirine, Bausteine für α,α‐disubstituierte α‐Aminosäuren in Heterocyclen‐ und Peptidsynthesen

3‐Amino‐2H‐Azirines. Synthons for α,α‐Disubstituted α‐Amino Acids in Heterocycle and Peptide Synthesis [New Analytical Methods (43)]

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Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways

Formation of Triazinium‐Imidothioate Zwitterions and Their Role as Key Intermediates for Novel S_N(ANRORC) Reaction Pathways