Conformational Properties of Aromatic Oligoamides Bearing Pyrrole Rings

Tojo, Yukiko; Urushibara, Ko; Yamamoto, S.; Mori, Hirotoshi; Masu, Hyuma; Kudo, Mayumi; Hirano, Tomoya; Azumaya, Isao; Kagechika, Hiroyuki; Tanatani, Aya

doi:10.1021/acs.joc.8b00349

Cited by 7 publications

(13 citation statements)

References 54 publications

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“…[54] Similarly to Nmethyl benzanilide, N-methyl-N-phenyl pyrrole 2-carboxamide exhibits predominantly the cis conformation but the proportion of cis conformer decreases in N-methyl-N-(4pyrrole) benzamide as demonstrated by 1 H NMR at low temperature in CD 2 Cl 2 . [20] A cis to trans switching effect induced by an environmental change (solvent or pH) was demonstrated by Okamoto and co-workers for N-methyl aromatic amides containing 2,6-disubstituted pyridine (Figure 6). [17] The protonation of the pyridyl ring under acidic conditions leads to a pyridinium core which is able to stabilize the trans conformation through the establishment of hydrogen-bonding with the oxygen of the adjacent carbonyl group.…”

Section: Local Conformational Preferences Of Nn-disubstituted Amidesmentioning

confidence: 89%

“…[19] Tanatani and co-workers have recently explored the conformational preferences of the N-alkylated amide bonds on the pyrrole group in heterooligomers containing both pyrrole and arene rings. [20] More related to N-alkylated benzamides, oligomeric Nsubstituted aminomethyl benzamides, or arylopeptoids, possess a backbone-methylene group adjacent to the phenyl ring. In connection with their pioneering work on peptoids, [14] Zuckermann and co-workers briefly mentioned the synthesis of such oligomers in few patents back in the 1990's, [21] but arylopeptoids were further developed by other groups taking advantages of the great chemical diversity available by variation of the substituents on the nitrogen.…”

Section: Classes Of N-alkylated Aromatic Oligoamidesmentioning

confidence: 99%

“…[16b] This methodology was also employed by Tanatani to prepare N-methyl oligoamides with alternating arene and pyrrole rings but was less efficient. [20] Again, only one type of side chain was used to prepare the oligomer. To access longer oligomers, an efficient block-coupling approach was preferred as illustrated by Ueda and co-workers in the preparation of N-alkylated oligo(p-benzamide)s comprising up to sixteen residues.…”

Section: Monomer Synthesismentioning

confidence: 99%

“…[41] Interesting features were also obtained when combining pyrrole and phenyl rings in N-methyl aromatic oligoamides. [20] NMR studies in CD 2 Cl 2 showed that the N-methylated amide attached at the 2-position of the pyrrole ring predominantly adopted the cis conformation, while the cis/trans ratio decreased when the N-methylated amide bond was at the 4position of the pyrrole ring (Scheme 11). Chain-length and solvent dependent CD spectra reflected different folding properties than N-alkylated para-oligobenzamides, suggest-ing the presence of a combination of cis-amide bonds with an anti/syn conformational preference but this unique conformation has not yet been confirmed.…”

Section: Secondary Structuresmentioning

confidence: 99%

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N‐Alkylated Aromatic Poly‐ and Oligoamides

et al. 2021

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N-alkylated aromatic poly-and oligoamides are a particular class of abiotic foldamers that is deprived of the capability of forming intramolecular hydrogen-bonding networks to stabilize their tri-dimensional structure. The alkylation of the backbone amide nitrogen atoms greatly increases the chemical diversity accessible for aromatic poly-and oligoamides. However, the nature and the conformational preferences of the N,N-disubstituted amides profoundly modify the folding properties of these aromatic poly-and oligoamides. In this Review, representative members of this class of aromatic poly-and oligoamides will be highlighted, among them N-alkylated phenylene terephthalamides, benzanilides, pyridylamides, and aminomethyl benzamide oligomers. The principal synthetic pathways to the main classes of N-alkylated aromatic polyamides with narrow to broad molecular-weight distribution, or oligoamides with specific sequences, will be detailed and their foldameric properties will be discussed. The Review will end by describing the few applications reported to date and future prospects for the field.

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Section: Local Conformational Preferences Of Nn-disubstituted Amidesmentioning

confidence: 89%

Section: Classes Of N-alkylated Aromatic Oligoamidesmentioning

confidence: 99%

Section: Monomer Synthesismentioning

confidence: 99%

Section: Secondary Structuresmentioning

confidence: 99%

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N‐Alkylated Aromatic Poly‐ and Oligoamides

et al. 2021

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“…Tojo et al synthesized the pyrrole-containing amides and their oligomers, and investigated their conformations in solution and in the crystalline state. [92] Compared with known foldamers with cis-amide conformation, oligoamides bearing a pyrrole ring displayed different dynamic folding properties. Urushibara et al reported the synthesis of alternately N-alkylated aromatic amide oligomers.…”

Section: Helical Polyamidesmentioning

confidence: 99%

Preparation and Chiral Applications of Optically Active Polyamides

Zhong

Deng

2021

Macromol. Rapid Commun.

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Chirality is omnipresent in nature and plays vital roles in living organism, and has become a hot research topic across multidisciplinary fields including chemistry, biology, physics, and material science. Meanwhile, polyamides constitute an important class of polymers and have received significant attention owing to their outstanding properties and wide-ranging applications in many areas. Judiciously introducing chirality into polyamides will undoubtedly obtain attractive chiral polymers, namely, optically active polyamides. This review describes the preparation methods of chiral polyamides, including solution polycondensation, interfacial polycondensation, ring-open polymerization, and others; the newly emerging categories of chiral polyamides, i.e., helical polyamides, chiral polyamide-imides, are also presented. The applications of optically active polyamides in chiral research fields including asymmetric catalysis, membrane separation, and enantioselective crystallization are also summarized. In addition, current challenges in chiral polyamides are further presented and future perspectives in the field are proposed. Preparation of Chiral Polyamides Solution PolycondensationSolution condensation polymerization is one of the most common methods to prepare chiral polyamides. Yoshikawa and

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Conformational Properties of Aromatic Amides Bearing Imidazole Ring and Acid-Induced Trans–Cis Amide Switching

et al. 2022

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Aromatic amides bearing secondary amide bond exist in trans conformation both in the crystal and in solution, whereas the conformation of the N-methylated derivatives is cis in the crystal and predominantly cis in various solvents. The cis conformational preference of N-alkylated benzanilide provides access to aromatic foldamers such as oligo(N-alkyl-p-benzamide)s, which adopt dynamic helical structures. Here, the conformational properties of imidazole-substituted amide in the crystal and in solution were examined. Imidazole-substituted amides 2a and 4a existed mainly in the cis conformation in solution. The ratio of the cis conformer of N-methyl-N-(1-methyl-1H-imidazol-4-yl)benzamide (4a) was smaller than that of N,1-dimethyl-N-phenyl-1H-imidazole-2-carboxamide (2a) or N-methylbenzanilide, but the introduction of a substituent strongly affected the conformer ratio. Compounds 6a and 7a bearing an electron-withdrawing group on the imidazole ring existed predominantly in trans form. On the other hand, the introduction of an electron-withdrawing group on the phenyl ring or a bulky substituent on the amide nitrogen of 4a increased the ratio of cis conformer. Further, the major conformer of N-alkylated N-imidazolylamides was switched from cis to trans by the addition of acid. These results suggest that imidazole-substituted amides might be applicable as conformational switches in aromatic foldamers to enable environment-dependent structural change.

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Conformational Properties of Aromatic Oligoamides Bearing Pyrrole Rings

Cited by 7 publications

References 54 publications

N‐Alkylated Aromatic Poly‐ and Oligoamides

N‐Alkylated Aromatic Poly‐ and Oligoamides

Preparation and Chiral Applications of Optically Active Polyamides

Conformational Properties of Aromatic Amides Bearing Imidazole Ring and Acid-Induced Trans–Cis Amide Switching

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