Reactions of carbamylimidazoles with nucleophiles - an example of an intramolecular acyl transfer reaction

Ehler, Kenneth W.

doi:10.1021/jo00880a031

Cited by 18 publications

(14 citation statements)

References 3 publications

(6 reference statements)

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“…The speculation that NCAs might have played a role in molecular evolution on the early Earth is about thirty years old, [303][304] but experimental data supporting this speculation were lacking for a long time. However, three series of results meanwhile lend a certain credibility to the speculation that NCAs might have been involved in prebiotic evolution.…”

Section: Ncas and The Hypothesis Of Molecular Evolutionmentioning

confidence: 99%

Polypeptides and 100 Years of Chemistry of α‐Amino Acid N‐Carboxyanhydrides

2006

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Syntheses and polymerizations of alpha-amino acid N-carboxyanhydrides (NCAs) were reported for the first time by Hermann Leuchs in 1906. Since that time, these cyclic and highly reactive amino acid derivatives were used for stepwise peptide syntheses but mainly for the formation of polypeptides by ring-opening polymerizations. This review summarizes the literature after 1985 and reports on new aspects of the polymerization processes, such as the formation of cyclic polypeptides or novel organometal catalysts. Polypeptides with various architectures, such as diblock, triblock, and multiblock sequences, and star-shaped or dendritic structures are also mentioned. Furthermore, lyotropic and thermotropic liquid-crystalline polypeptides will be discussed and the role of polypeptides as drugs or drug carriers are reviewed. Finally, the hypothetical role of NCAs in molecular evolution on the prebiotic Earth is discussed.

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Section: Ncas and The Hypothesis Of Molecular Evolutionmentioning

confidence: 99%

Polypeptides and 100 Years of Chemistry of α‐Amino Acid N‐Carboxyanhydrides

2006

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“…Die Spekulation, dass NCAs eine Rolle in der molekularen Evolution gespielt haben könnten, ist etwa 30 Jahre alt, [303,304] aber Experimente, die dieser Spekulation eine nennenswerte Wahrscheinlichkeit zugestanden hätten, fehlten für lange Zeit. Mittlerweile gibt es jedoch drei Arbeitsrichtungen mit Ergebnissen, die einer Rolle der NCAs in der präbiotischen Evolution eine erhebliche Glaubwürdigkeit verleihen.…”

Section: Ncas Und Die Hypothese Der Molekularen Evolutionunclassified

Polypeptide und 100 Jahre Chemie der α‐Aminosäure‐N‐carboxyanhydride

Kricheldorf

2006

Angewandte Chemie

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Synthese und Polymerisation von α‐Aminosäure‐N‐carboxyanhydriden (NCAs) wurden erstmals im Jahre 1906 von Herrmann Leuchs beschrieben. Seit dieser Zeit wurden diese cyclischen, sehr reaktiven α‐Aminosäurederivate mehrfach zur schrittweisen Peptidsynthese eingesetzt, sie wurden aber vor allem zur Herstellung von Polypeptiden durch ringöffnende Polymerisation (ROP) verwendet. Es werden nun neue Aspekte der ringöffnenden Polymerisation diskutiert, z. B. die Verwendung neuartiger metallorganischer Initiatoren oder die Entstehung cyclischer Polypeptide. Des Weiteren werden Architekturen wie Diblock‐, Triblock‐ und Multiblockcopolymere sowie sternförmige oder hochverzweigte Polypeptide vorgestellt. Ferner werden lyotrope und thermotrope Polypeptide sowie die Verwendung von Polypeptiden als Pharmaka oder Pharmakaträger besprochen. Schließlich wird die Rolle von NCAs im Konzept der molekularen Evolution diskutiert.

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“…These features are consistent with a polymerization mechanism involving low concentrations of an N-carboxyanhydride intermediate as mentioned above for the conversion of carbamate derivatives of aminoacids with good leaving groups. The conversion of carbamylimidazole intermediate 23b into NCA is possible because of the easy elimination of imidazole giving isocyanate 24, but the fact that a similar process was also observed with the N-methylated compound derived from sarcosine shows that acyl transfer via an additionelimination mechanism (path b of Scheme 37) is also possible [126].…”

Section: Scheme 31mentioning

confidence: 95%

“…in stereoselection studies [125]. Even though their capabilities as activated peptide monomers in this field had been mentioned earlier [126,127], it is only during the last decade that several plausible pathways have been proposed for the prebiotic formation of N-carboxyanhydrides as well as pathways in which they are clearly identified or presumed intermediates. We will show in the following that they could even be considered as a universal activated form of amino acids.…”

Section: Polymerization Of N-carboxy Amino Acid Anhydrides (Ncas)mentioning

confidence: 99%