syn-anti Isomer Determination of 2,4-Dinitrophenylhydrazones and Semicarbazones by N.m.r.

Karabatsos, Gerasimos J.; Graham, John D.; Vane, Floie M.

doi:10.1021/ja00864a015

Cited by 99 publications

(36 citation statements)

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“…H-3 of the latter anomer exhibits coupling with I3C-1 of 5.7 Hz, whereas H-2 of the a-anomer shows no such coupling (Table 1 ). Although these findings contrast with the fact that geminal 13C-H splitting of about 4 Hz is seen in the spectra of various acyclic alkyl derivatives (15), it is possible that there is a substantial difference between 5 and 6 in the angle subtended by l3C1-C2-H,.…”

Section: Vicinal ' Jc-h Co~cplingmentioning

confidence: 70%

“…Rotamer 34, in which 0 -5 is tt.rrns to one H-6, is therefore a plausible major contributor. In view of the geminal coupling differences between the anomers of D-glucose-l-13C and of the fact that values for geminal coupling in alkyl derivatives are commonly 4-5 Hz (15)(16)(17)(18)(19), the orientations represented by 32 and 33 would both be expected to give rise to perhaps a 4-5 Hz splitting of the H-5 signal due to interaction with "C-6. Only a small coupling (2 Hz) attributable to the latter source is found in the spectrum of 13, and none is detected in the spectrum of 14.…”

Section: I;'mentioning

confidence: 99%

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Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Schwarcz¹,

Perlin²

1972

Can. J. Chem.

162

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The effect of changes in the relative orientation of vicinal and geminal 13C and 1H nuclei, and in the disposition of adjacent substituents, on coupling between these nuclei has been examined with a variety of 13C-labelled carbohydrates. Compounds synthesized for this purpose include derivatives of D-glucose-1- and -6-13C and L-idose-6-13C, and related lactones, and the measurements have been made with p.m.r. spectra of these compounds. Vicinal 13C-1H coupling, both through C—C and C—O bonds shows an orientational dependance analogous to that for protons: i.e., dihedral angles of 60–100° are associated with smaller coupling (0–3 Hz) than angles of 140–180° (4.5–5.5 Hz); sp2 carbon produces splittings of almost twice these values. The observed spacing is smaller when an oxygen atom is in the plane of the coupling pathway than when out of plane, both for vicinal and geminal 13C–1H interactions, and the presence of an extra oxygen also may have a notable impact on the geminal interaction. A study of rotational isomerism in these compounds indicates that the characteristics of coupling between 13C and 1H nuclei may fruitfully be compared with those of H–H coupling in the analysis of such dynamic systems.

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Section: Vicinal ' Jc-h Co~cplingmentioning

confidence: 70%

Section: I;'mentioning

confidence: 99%

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Schwarcz¹,

Perlin²

1972

Can. J. Chem.

162

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“…A reação das benzamidoximas (32) com cloreto de metiloxalila originou os ésteres metílicos (33), que, após tratamento com hidrato de hidrazina, produziram as hidrazidas (34). Estas, por condensação catalisada por ácido com os aldeídos adequados, produziram a nova série heterocíclica de derivados NAH (30).…”

Section: Esquema 16unclassified

A química medicinal de N-acilidrazonas: novos compostos-protótipos de fármacos analgésicos, antiinflamatórios e anti-trombóticos

et al. 2002

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Rio de Janeiro RJRecebido em 1/3/01; aceito em 13/6/01 MEDICINAL CHEMISTRY OF N-ACYLHYDRAZONES: NOVEL LEAD-COMPOUNDS OF ANALGESIC, ANTIINFLAMMATORY AND ANTITHROMBOTIC DRUGS. In this article are described new bioactive N-acylhydrazone (NAH) derivatives, structurally designed as optimization of aryl hydrazones precursors planned by molecular hybridization of two 5-lipoxigenase inhibitors, e.g. CBS-1108 and BW-755c. The analgesic, antiedematogenic and anti-platelet aggregating profile of several isosteric compounds was investigated by using classic pharmacological assays in vivo and ex-vivo, allowing to identify new potent peripheric analgesic lead, a new anti-inflammatory and an antithrombotic agent. During this study was discovered dozen of active NAH compounds clarifying the structure-activity relationship for this series of NAH derivatives, indicating the pharmacophore character of the N-acylhydrazone functionality.Keywords: bioactive N-acylhydrazones derivatives; antiinflammatory, analgesic and antithrombotic properties; molecular hybridization and bioisosterism in drug design. INTRODUÇÃOA Química Medicinal estuda as razões moleculares da ação dos fármacos 1 de maneira a descrever a relação entre a estrutura química e a atividade farmacológica, hierarquizando as diferentes contribuições funcionais. No contexto inverso, inclui-se o planejamento e o desenho estrutural de novas substâncias que possuam propriedades farmacoterapêuticas úteis, capazes de representarem novas entidades químicas, candidatas a protótipos de novos fármacos de uso seguro. Esta complexa tarefa envolve múltiplos fatores, responsáveis pela resposta terapêutica desejada e decorrentes da complexidade dos sistemas biológicos, abrangendo diversos conceitos de diferentes disciplinas, não podendo ser cumprida aleatoriamente. Heuristicamente para a identificação de um novo composto-protóti-po ou uma nova entidade química que possa representar novo candidato a fármaco, elege-se o melhor alvo-farmacológico para aquela aplicação terapêutica e, em função do nível de conhecimento estrutural disponível sobre este receptor, identifica-se a melhor estratégia para a construção da arquitetura molecular do novo ligante desejado. Diversas estratégias modernas de desenho molecular de novos protótipos são conhecidas 2 , em função do mecanismo de ação pretendido, seja inibição enzimática, reversível ou não, ou agonismo/antagonismo, competitivo ou não, do receptor, que dependem do nível de conhecimento de sua topografia.O conhecimento da topografia molecular tridimensional (3D) do receptor, especialmente do sítio de interação, permite o desenho de inibidores enzimáticos ou de antagonistas/agonistas de receptores, por processos de complementaridade molecular planejada, 3 que podem, por sua vez, discriminar entre interações ou ligações covalentes 4 . Quando não se conhece a estrutura do biorreceptor-alvo, a estratégia mais empregada fundamenta-se na variação da similaridade molecular do agonista natural de forma a que se identifique um análogo ativo 5 , reflexo de s...

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“…In all experiments, the 1 H-and 13 C-NMR spectra were recorded at definite time intervals starting from the moment of dissolution until the end of transformations. In addition, the structure of the compounds under study in the crystalline state was confirmed by solid-phase high-resolution [14]. The signals of the Z'-isomer of this group are disposed at lower field than the analogous signals of the E'-isomer.…”

Section: Resultsmentioning

confidence: 93%

Ring-Chain Tautomerism of the Condensation Products of 2-Mercaptobenzohydrazide with Aliphatic and Aromatic Aldehydes: Influence of Electronic and Steric Factors

Еrshov¹,

Lagoda²,

Vasil'eva³

et al. 2017

OALib

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It has been shown by 1 H and 13 C NMR spectroscopy that 2-mercaptobenzoylhydrazones of aliphatic and aromatic aldehydes exist in solution as tautomeric mixtures of linear and cyclic benzo-1,3,4-thiadiazepine forms. The linear hydrazone form is represented by (E,E')-and (E,Z')-conformational isomers, differing in the disposition relative to the amide C-N bond. Growing bulk of the alkyl substituent at the C=N bond of the aliphatic aldehydes derivatives decreases the fraction of the cyclic tautomer; therewith the logarithms of the constants of the chain-ring tautomeric equilibrium correlate with the E S steric constants of the alkyl substituents. In the series of the aromatic aldehydes 2-mercaptobenzoylhydrazones the linear tautomer prevails, and the logarithms of the tautomeric equilibrium constants K T correlate with the σ-constants of the substituents in the aromatic nucleus.

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syn-anti Isomer Determination of 2,4-Dinitrophenylhydrazones and Semicarbazones by N.m.r.

Cited by 99 publications

References 0 publications

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

A química medicinal de N-acilidrazonas: novos compostos-protótipos de fármacos analgésicos, antiinflamatórios e anti-trombóticos

Ring-Chain Tautomerism of the Condensation Products of 2-Mercaptobenzohydrazide with Aliphatic and Aromatic Aldehydes: Influence of Electronic and Steric Factors

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syn-anti Isomer Determination of 2,4-Dinitrophenylhydrazones and Semicarbazones by N.m.r.

Cited by 99 publications

References 0 publications

Orientational Dependance of Vicinal and Geminal 13C–1H Coupling

Orientational Dependance of Vicinal and Geminal 13C–1H Coupling

A química medicinal de N-acilidrazonas: novos compostos-protótipos de fármacos analgésicos, antiinflamatórios e anti-trombóticos

Ring-Chain Tautomerism of the Condensation Products of 2-Mercaptobenzohydrazide with Aliphatic and Aromatic Aldehydes: Influence of Electronic and Steric Factors

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Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling