Substituent effects on the stability of carbodiimides

Tahmassebi, Daryoush

doi:10.1039/b006901i

Cited by 16 publications

(8 citation statements)

References 34 publications

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“…Nonetheless, such a strategy should be cautiously pursued since the stability of imine function increases when nucleophilicity decreases due to the stabilizing effect of electropositive substituents on the C=N double bond (Tahmassebi 2001). This implies that carnosine derivatives endowed with relatively basic amines will lose their selectivity by trapping even physiological carbonyls.…”

Section: Carnosine Bioavailability and Metabolic Fate In Humansmentioning

confidence: 98%

Transforming dietary peptides in promising lead compounds: the case of bioavailable carnosine analogs

Vistoli

Carini

2012

Amino Acids

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The ability of carnosine to prevent advanced glycoxidation end products (AGEs) and advanced lipoxidation end products (ALEs) formation, on the one hand, and the convincing evidence that these compounds act as pathogenetic factors, on the other hand, strongly support carnosine as a promising therapeutic agent for oxidative-based diseases. The mechanism/s by which carnosine inhibits AGEs and ALEs is still under investigation but an emerging hypothesis is that carnosine acts by deactivating the AGEs and ALEs precursors and in particular the reactive carbonyl species (RCS) generated by both lipid and sugar oxidation. The ability of carnosine to inhibit AGEs and ALEs formation and the corresponding biological effects has been demonstrated in several in vitro studies and in some animal models. However, such effects are in line of principle, limited in humans, due to the effect of serum carnosinase (absent in rodents), which catalyzes the carnosine hydrolysis to its constitutive amino acids. Such a limitation has prompted a great interest in the design of carnosine derivatives, which maintaining (or improving) the reactivity with RCS, are more resistant to carnosinase. The present paper intends to critically review the most recent studies oriented to obtaining carnosine derivatives, optimized in terms of reactivity with RCS, selectivity (no reaction with physiological aldehydes) and the pharmacokinetic profile (mainly through an enhanced resistance to carnosinase hydrolysis). The review also includes a brief description of AGEs and ALEs as drug targets and the evidence so far reported regarding the ability of carnosine as inhibitor of AGEs and ALEs formation and the proposed reaction mechanisms.

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Section: Carnosine Bioavailability and Metabolic Fate In Humansmentioning

confidence: 98%

Transforming dietary peptides in promising lead compounds: the case of bioavailable carnosine analogs

Vistoli

Carini

2012

Amino Acids

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“…Both isomers are separated by only 1 kcal mol À1 and can be regarded as conformers with respect to rotation about the N(CN) À CHO bond ( Synthesis and properties of alkali dicyanoamides have been studied intensively over the last decades. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] We want to focus here on covalently bound dicyanoamides, for which little is known. Alkali dicyanoamides are stable in neutral aqueous solution; however, they tend to polymerize at lower pH values.…”

Section: Synthesis Properties and Structure Of Phenylformylcyanoamidementioning

confidence: 99%

“…Moreover, the thermal stability increases along the series EMIM + X À < BMIM + X À < HMIM + X À . Slow decomposition arising from hydrolysis of the formyl-based ILs is observed when exposed to air [Equations (11) and (12)].…”

Section: Ionic Liquidsmentioning

confidence: 99%

Salts and Ionic Liquids of Resonance Stabilized Amides

Brand

Martens

Mayer

et al. 2009

Chemistry An Asian Journal

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The synthesis, structure, and bonding of alkali salts of resonance stabilized amides, such as diformylamide (dfa), formylcyanoamide (fca), nitrocyanoamide (nca), and for comparision, the well-known dicyanoamide (dca), are discussed on the basis of experimental and theoretical data. The first structural reports of K(18-crown-6)+dfa-, K(18-crown-6)+fca-, Na+nca-, and Li(TMEDA)+dca- are presented. Examination of the X-ray data reveals almost planar anions with strong cation-anion interactions resulting in network-like structures in the solid state. For comparison, the X-ray structures of covalently bound phenyldicyanoamide and diformamide are also discussed. The thermal behavior of the alkali salts of these amides is studied by thermoanalytical experiments. Moreover, several novel ionic liquids based on resonance stabilized amides have been prepared and were fully characterized, namely the dfa, fca, and nca salts of EMIM (1-ethyl-3-methyl-imidazolium), BMIM (1-butyl-3-methyl-imidazolium), and HMIM (1-hexyl-3-methyl-imidazolium). Most of them are liquid at room temperature, except BMIM+fca- that melts at 32 degrees C. These ionic liquids are neither heat nor shock sensitive, are thermally stable up to over 200 degrees C, and can be prepared easily in large quantities.

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“…27 Ab initio density functional theory calculations have been used to estimate the geometries and energies of monosubstituted carbodiimides, RN=C=NH, and imines, RN=CH 2 . 28 Electronegative substituents destabilize carbodiimides whereas electropositive substituents stabilize them. Strongly electropositive groups give a linear geometry, owing to charge repulsion and a preference for sp-hybridization at nitrogen.…”

Section: Iminesmentioning

confidence: 99%

“…47 ᭺ de cis-Fused furano-and pyrano-benzopyrans (28, n = 1, 2) can be prepared in high diastereoselectivity from o-hydroxybenzaldimines and 2,3-dihydrofuran or 3,4dihydropyran respectively, using LiBF 4 catalysis. 48 (28) ( 30)…”

Section: ᭺ Dementioning

confidence: 99%

Reactions of Aldehydes and Ketones and their Derivatives

Knipe¹

2015

Organic Reaction Mechanisms Series

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Formation and Reactions of Acetals and Related SpeciesThe α,α -dihaloketone 2,4-dichlorobicyclo[3.2.1]oct-6-en-3-one (1, a mixture of ax-ax, ax-eq, and eq-eq isomers) undergoes a 1,3-transposition in alkoxide-alcohol media to give α-ketoacetals (2, R = CH 3 , CH 2 CF 3 , −CH 2 CH 2 −), all of which are readily hydrolysable to the corresponding α-diones. 1 The acetal is favoured by an O,O-geminal stabilization relative to the α,α -dialkoxy ketone: none of the latter

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Substituent effects on the stability of carbodiimides

Cited by 16 publications

References 34 publications

Transforming dietary peptides in promising lead compounds: the case of bioavailable carnosine analogs

Transforming dietary peptides in promising lead compounds: the case of bioavailable carnosine analogs

Salts and Ionic Liquids of Resonance Stabilized Amides

Reactions of Aldehydes and Ketones and their Derivatives

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