Helical aromatic urea and guanidine

Tanatani, Aya; Kagechika, Hiroyuki; Azumaya, Isao; Fukutomi, Ryuuta; Ito, Yuji; Yamaguchi, Kentaro; Shudo, Koichi

doi:10.1016/s0040-4039(97)00922-2

Cited by 71 publications

(57 citation statements)

References 27 publications

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“…[43] The facile transformation of thioureas into guanidiniums [44] and the importance of this moiety in biology, medicinal chemistry, drug delivery, and supramolecular structures also suggests application of (thio)urea hybrid oligomers as synthetic intermediates towards the elaboration of oligomers incorporating N,N'-linked guanidinium units at selected positions in the main chain. [45] The synthesis, and exploration of the folding and chemical properties of these novel urea/guanidinium hybrid backbones will be reported in due course.…”

Section: Resultsmentioning

confidence: 99%

Isosteric Substitutions of Urea to Thiourea and Selenourea in Aliphatic Oligourea Foldamers: Site‐Specific Perturbation of the Helix Geometry

Nelli

Antunes

Salaün

et al. 2014

Chemistry A European J

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Nearly isosteric oxo to thioxo substitution was employed to interrogate the structure of foldamers with a urea backbone and explore the relationship between helical folding and hydrogen-bonding interactions. A series of oligomers with urea bonds substituted by thiourea bonds at discrete or all positions in the sequence have been prepared and their folding propensity was studied by using a combination of spectroscopic methods and X-ray diffraction. The outcome of oxo to thioxo replacements on the helical folding was found to depend on whether central or terminal ureas were modified. The canonical helix geometry was not affected upon insertion of thioureas close to the negative end of the helix dipole, whereas thioureas close to the positive pole were found to increase the terminal flexibility and cause helix fraying. Perturbation was amplified when a selenourea was incorporated instead, leading to a structure that is only partly folded.

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Section: Resultsmentioning

confidence: 99%

Isosteric Substitutions of Urea to Thiourea and Selenourea in Aliphatic Oligourea Foldamers: Site‐Specific Perturbation of the Helix Geometry

Nelli

Antunes

Salaün

et al. 2014

Chemistry A European J

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“…[19] Shudo and co-workers, [20] and later Clayden et al [21] exploited this preference in the design of the helical oligourea foldamers 9 ( Figure 2) whose helicity can be controlled over one or two turns of the helix in solution, [22] thus allowing relayed remote stereochemical control. [23] Slow rotation in a N,N'-diaryl urea [24] generates atropisomeric structures.…”

Section: Conformation Of Substituted Ureasmentioning

confidence: 99%

The Urea Renaissance

2011

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Over the last decade the use of urea derivatives as useful reagents, catalysts, and structural features in organic chemistry has increased rapidly. They now find utility as hydrogen-bond donors in organocatalysts and anion transporters, as important scaffolds in supramolecular chemistry, as lithiation directors, amination substrates, and promoters of metalation, and as substrates for novel rearrangement reactions. Highlighted herein is the remarkably rapid and recent development of the chemistry of ureas, which for many years had been considered unreactive, intractable, and of little value.

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“…This is clearly at odds with the reported well-defined helical conformations of more extended oligoureas. 9 Further work aimed at understanding the origin of the conformation of helical oligoureas is under way.…”

Section: Fig 3 Interconverting Conformers Of Ureas 3a-kmentioning

confidence: 99%

Conformation and stereodynamics of 2,2′-disubstituted N,N′-diaryl ureas

et al. 2008

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Except in the most hindered of cases, N,N'-diaryl N,N'-dimethyl ureas adopt a conformation with the two aryl rings disposed cis to one another. Variable temperature NMR studies reveal the rate at which the Ar-N bonds rotate as well as the conformational preference of ortho disubstituted ureas in which more than one cis orientation is possible. In general, a conformation in which the aryl rings lie close in space but with their most bulky 2-substituents aligned anti is preferred, but with particularly bulky 2-substituents, conformations in which one of the aryl rings points away from the other may also be populated.

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Helical aromatic urea and guanidine

Cited by 71 publications

References 27 publications

Isosteric Substitutions of Urea to Thiourea and Selenourea in Aliphatic Oligourea Foldamers: Site‐Specific Perturbation of the Helix Geometry

Isosteric Substitutions of Urea to Thiourea and Selenourea in Aliphatic Oligourea Foldamers: Site‐Specific Perturbation of the Helix Geometry

The Urea Renaissance

Conformation and stereodynamics of 2,2′-disubstituted N,N′-diaryl ureas

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