scholarly journals On the Hydration State of Amino Acids and Their Derivatives at Different Ionization States: A Comparative Multinuclear NMR and Crystallographic Investigation

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Charalampos G. Pappas ◽  
Andreas G. Tzakos ◽  
Ioannis P. Gerothanassis
Keyword(s):  
Amino Acids ◽  
Hydrogen Bond ◽  
Relaxation Times ◽  
Carboxylate Group ◽  
Ionization State ◽  
Carboxylic Groups ◽  
Hydration Model ◽  
Structure Databases ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

2D, 13C, 14N, and 17O NMR and crystallographic data from the literature were critically evaluated in order to provide a coherent hydration model of amino acids and selected derivatives at different ionization states. 17O shielding variations, longitudinal relaxation times (T1) of 2D and 13C and line widths (Δν1/2) of 14N and 17O, may be interpreted with the hypothesis that the cationic form of amino acids is more hydrated by 1 to 3 molecules of water than the zwitterionic form. Similar behaviour was also observed for N-acetylated derivatives of amino acids. An exhaustive search in crystal structure databases demonstrates the importance of six-membered hydrogen-bonded conjugated rings of both oxygens of the α-carboxylate group with a molecule of water in the vicinity. This type of hydrogen bond mode is absent in the case of the carboxylic groups. Moreover, a considerable number of structures was identified with the propensity to form intramolecular hydrogen bond both in the carboxylic acid (NH⋯O=C) and in the carboxylate (−) ionization state. In the presence of bound molecules of water this interaction is significantly reduced in the case of the carboxylate group whereas it is statistically negligible in the carboxylic group.

Preparation of ketimine derivatives of amino acids for peptide synthesis

1974 ◽  
Vol 27 (9) ◽  
pp. 2047 ◽  
Author(s):  
B Halpern ◽  
AP Hope
Keyword(s):  
Amino Acids ◽  
Hydrogen Bond ◽  
Acid Hydrolysis ◽  
Peptide Synthesis ◽  
Room Temperature ◽  
Mild Conditions ◽  
Protein Amino Acids ◽  
Intramolecular Hydrogen ◽  
Derivatives Of ◽  
Strong Intramolecular Hydrogen Bond

Condensates of some 2-hydroxyaryl ketones with protein amino acids have been prepared. The reaction has been shown to proceed without racemization and the derivatives have been isolated as free acids. Their unusual stability is ascribed to the presence of a strong intramolecular hydrogen bond. The N-arylmethylene function is cleaved under mild conditions of acid hydrolysis. Ketimines derived from D-phenylglycine decarboxylate at room temperature.

scholarly journals Dimethylammonium 2,4,5-tricarboxybenzoate: an example of the decarbonylation ofN,N-dimethylformamide in the presence of a metal and a benzenepolycarboxylic acid. Is zirconium(IV) theTsotsi?

2016 ◽  
Vol 72 (11) ◽  
pp. 1521-1525 ◽  
Author(s):  
S. T. Hulushe ◽  
E. C. Hosten ◽  
G. M. Watkins
Keyword(s):  
Hydrogen Bond ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Carboxylate Group ◽  
Tetracarboxylic Acid ◽  
Asymmetric Unit ◽  
Dimensional Network ◽  
Metal Organic ◽  
Unexpected Product ◽  
Intramolecular Hydrogen

The title salt, C2H8N+·C10H5O8−, was the unexpected product of an attempt to prepare a ZrIVmetal–organic framework with benzene-1,2,4,5-tetracarboxylic acid (1,2,4,5-H3B4C). In the reaction, the DMF solvent has been decarbonylated, forming the dimethylammonium cation, with one proton lost from the tetracarboxylic acid. It is proposed that the ZrIVsalt acts as aTsotsior robber, plundering CO from the DMF molecule. The resulting salt crystallizes with two cations and two anions in the asymmetric unit. An intramolecular hydrogen bond forms between a carboxylic acid substituent and the carboxylate group of each of the monodeprotonated (1,2,4,5-H3B4C−) anions. In the crystal, an extensive array of O—H...O, N—H...O and C—H...O hydrogen bonds generates a three-dimensional network, with columns of cations and anions forming along thebaxis.

Hydrogen bonding, configuration and conformation of substituted α-oxo oximes and hydrazones

1979 ◽  
Vol 44 (8) ◽  
pp. 2494-2506 ◽  
Author(s):  
Otto Exner ◽  
Jorga Smolíková ◽  
Václav Jehlička ◽  
Ahmad S. Shawali
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Intramolecular Hydrogen Bond ◽  
Benzene Solution ◽  
Dipole Moments ◽  
H Nmr ◽  
Intramolecular Hydrogen ◽  
Derivatives Of ◽  
Configuration And Conformation

Substituted 2-bromo-1-phenylglyoxal 2-phenylhydrazones IIIa-f exist in tetrachloromethane or benzene solutions prevailingly in E-configuration and in conformation A with an intramolecular hydrogen bond. The latter was evidenced by the N-H valence frequency at 3 290 cm-1 and by 1H NMR shifts with reference to derivatives without a carbonyl group - α-chlorobenzaldehyde phenylhydrazones V. From dipole moments of IIIa-d, measured in benzene solution, the contribution of the hydrogen bond (μH) was evaluated to 17 . 10-30 C m. This quantity is twice larger than in any other reported compound but the direction of the vector is as usual: approximately from H to N. In structurally similar derivatives of hydroxylamine, substituted 2-phenylglyoxylhydroximoyl chlorides IVa-d, no intramolecular hydrogen bond was detected; the dipole moments found were interpreted in terms of the Z-configuration and the prevailing conformation G.

Triorganoblei- und Triorganozinnderivate von Hydroxyaminosäuren und O-Acetylserin / Triorganolead and Triorganotin Derivatives of Hydroxyamino Acids and of O-Acetylserine

1991 ◽  
Vol 46 (3) ◽  
pp. 270-274 ◽  
Author(s):  
Brigitte Mundus-Glowacki ◽  
Friedo Huber
Keyword(s):  
Amino Acids ◽  
Carboxylate Group ◽  
Carboxylate Groups ◽  
Hydroxyamino Acids ◽  
Derivatives Of

Bis(triphenyllead) compounds (Ph3Pb)2A [H2A = H2Ser (= L-serine), H2Tyr (= L-tyrosine), H2Phoser (= phosphorylserine)], R3PbAcSer (HAcSer = O-acetylserine; R = Ph, Me) and Ph3SnAcSer have been prepared from R3MOH and the appropriate amino acids. From IR data it is inferred that all compounds are polymeric, and that (Ph3Pb)2A (A = Ser, Tyr) and Me3PbAcSer contain unsymmetrically bridging carboxylate groups and coordinating NH2. For (Ph3Pb)2Phoser a structure with a monodentate carboxylate group and intermolecular coordination of Pb by an NH2- and a P=O-group is proposed. The molecules of Ph3MAcSer (M = Pb, Sn) containing monodentate carboxylate groups are bridged by acetyl-C=O groups.

scholarly journals Intramolecular hydrogen bond directed distribution of conformational populations in the derivatives of N′-benzylidenebenzohydrazide

2019 ◽  
Vol 43 (33) ◽  
pp. 13134-13142 ◽  
Author(s):  
Neeru Arya ◽  
Sandeep Kumar Mishra ◽  
N. Suryaprakash
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bond ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The extensive NMR investigations reveal the presence of E-isomers in the derivative of N′-benzylidenebenzohydrazide. The different conformer populations are controlled by the strength of intramolecular hydrogen bonds.

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