scholarly journals Approaches to α-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

2012 ◽  
Vol 8 ◽  
pp. 1393-1399 ◽  
Author(s):  
Sosale Chandrasekhar ◽  
V Mohana Rao
Keyword(s):  
Amino Acids ◽  
Peptide Synthesis ◽  
Carboxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Confirmation ◽  
Amino Protection

The titled approaches were effected with various 2-substituted benzoylacetic acid oximes 3 (Beckmann) and 2-substituted malonamic acids 9 (Hofmann), their carboxyl groups being masked as a 2,4,10-trioxaadamantane unit (an orthoacetate). The oxime mesylates have been rearranged with basic Al2O3 in refluxing CHCl3, and the malonamic acids with phenyliodoso acetate and KOH/MeOH. Both routes are characterized by excellent overall yields. Structure confirmation of final products was conducted with X-ray diffraction in selected cases. The final N-benzoyl and N-(methoxycarbonyl) products are α-amino acids with both carboxyl and amino protection; hence, they are of great interest in peptide synthesis.

scholarly journals Hydrogen bonding in melamine compounds of amino acids

2014 ◽  
Vol 70 (a1) ◽  
pp. C534-C534
Author(s):  
Nasreddine Ghouari ◽  
Nourreedine Benali-Cherif
Keyword(s):  
Amino Acids ◽  
Hydrogen Bonding ◽  
Nitric Acid ◽  
Organic Cation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hybrid Compounds ◽  
Amino Butyric Acid ◽  
3D Network ◽  
Bonding Electron

The theme of this work is part of the study of intermolecular interactions that hold the crystal structures of hybrid compounds based sulphuric acid, nitric acid, Melamine, Diethylamine, L-(+) - glutamic acid, DL-2-amino butyric acid. The aim of this work is to enlarge our laboratory researches [1-3] and methods in synthesis of new hybrid compounds consisting in organic cation(s) and mineral anion(s). We have obtained single crystals of a few samples after several trials and we plan to synthesize and characterize these crystals by X-ray diffraction, FTIR and Raman. The crystals structures allow us to study the 3D network hydrogen bonding, electron density and collect several other informations useful in FTIR and Raman studies of these hybrid compounds.

Metal Phenoxyalkanoic Acid Interactions. XXV. The Crystal Structures of (2-Formyl-6-Methoxyphenoxy)Acetic Acid and Its Zinc(II) Complex and the Lithium, Zinc(II) and Cadmium(II) Complexes of (2-Chlorophenoxy)Acetic Acid

1987 ◽  
Vol 40 (7) ◽  
pp. 1147 ◽  
Author(s):  
EJ Oreilly ◽  
G Smith ◽  
CHL Kennard ◽  
TCW Mak
Keyword(s):  
Acetic Acid ◽  
Crystal Structures ◽  
Free Acid ◽  
Rotational Symmetry ◽  
Carboxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Third ◽  
Planar Complex ◽  
Hydrogen Bonded

The crystal structures of (2-formyl-6-methoxyphenoxy)acetic acid (1), diaquabis [(2-formyl-6-methoxyphenoxy) acetato ]zinc(11) (2), tetraaquabis [(2-chlorophenoxy) acetato ]zinc(11) (3), triaquabis [(2-chlorophenoxy) acetato ]cadmium(11) dihydrate (4) and lithium (2-chloro- phenoxy )acetate 1.5 hydrate (5) have been determined by X-ray diffraction. The acid (1) forms centrosymmetric hydrogen-bonded cyclic dimers [O…0, 2.677(6) �] which are non-planar. Complex (2) is six-coordinate with two waters [Zn- Ow , 1.997(2) �] and four oxygens from two asymmetric bidentate carboxyl groups [Zn-O, 2.073, 2.381(2) �] completing a skew trapezoidal bipyramidal stereochemistry. Complex (5) is also six-coordinate but is octahedral, with two trans-related unidentate carboxyl oxygens [mean Zn-O, 2.134(9) �] and four waters [mean Zn-O, 2.081(9) �]. The seven-coordinate complex (4) has crystallographic twofold rotational symmetry relating two :symmetric bidentate acid ligands [ Cd -O, 2.26, 2 48(:) �] and two waters [ Cd -O, 2.34(2) �] while the third water lies on this axis [ Cd -O, 2.27(2) �]. In contrast to the monomers (2)-(4), complex (5) is polymeric with tetrahedral lithium coordinated to one water and three carboxylate oxygens [mean Li-0, 1.95(1) �]. The essential conformation of the free acid is retained in complexes (2), (3) and (4) but in (5), it is considerably changed.

Metallkomplexe mit biologisch wichtigen Liganden, CXLVI [1]. Bis(allyl)-N,O-α-Aminocarboxylat-Rhodium-Komplexe / Metal Complexes of Biologically Important Ligands, CXLVI [1]. Bis(allyl)-N,O-α-Aminocarboxylate-Rhodium Complexes

2002 ◽  
Vol 57 (7) ◽  
pp. 810-818 ◽  
Author(s):  
Walter Ponikwar ◽  
Peter Mayer ◽  
Wolfgang Beck
Keyword(s):  
Amino Acids ◽  
Metal Complexes ◽  
Dynamic Behaviour ◽  
Rhodium Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr

The reactions of [(η3-C3H5)2Rh-μ-Cl]2 with the anions of α-amino acids (glycine, L-alanine, L-valine, L-isoleucine, L-proline, L-phenylalanine, L-phenylglycine, L-thyrosine) afford the N,O-chelates (η3-C3H5)2Rh(α-amino carboxylate). For complex (η3-C3H5)2Rh(glycinate) dynamic behaviour in solution could be observed by 1H NMR. The structure of (η3-C3H5)2Rh(L-prolinate) was determined by X-ray diffraction.

scholarly journals X-ray diffraction and X-ray K absorption near edge studies of copper (II) complexes with amino acids

2017 ◽  
Vol 836 ◽  
pp. 012039
Author(s):  
P K Sharma ◽  
Ashutosh Mishra ◽  
Varsha Malviya ◽  
Rashmi Kame ◽  
P K Malviya
Keyword(s):  
Amino Acids ◽  
X Ray Diffraction ◽  
X Ray

Synthesis and Crystal Structure Determination of Cyclosporin H

2000 ◽  
Vol 65 (8) ◽  
pp. 1317-1328 ◽  
Author(s):  
Alexandr Jegorov ◽  
Ladislav Cvak ◽  
Aleš Husek ◽  
Petr Šimek ◽  
Anna Heydová ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Amino Acids ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Acid Catalyzed ◽  
Products Of Reaction ◽  
Cyclosporin H

Acid-catalyzed degradation of cyclosporin A was studied in various solvents and products of reaction were monitored by HPLC. Identification of amino acids and their chirality were determined after hydrolysis and derivatization by GC-MS. Cyclosporin H was isolated as the principal product and its structure was determined by X-ray diffraction: Cyclosporin H- diethyl ether-water (1 : 0.5 : 1) crystallizes in the monoclinic space group I2 with a = 12.338(2) Å, b = 18.963(2) Å, c = 34.074(3) Å, β = 96.47(2)°, Z = 4, and V = 7 921.4(17) Å3.

Conformational study of the 3,6-dihydro-2H-1,4-oxazin-2-one fragment in 8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione stereoisomers

2017 ◽  
Vol 73 (7) ◽  
pp. 556-562
Author(s):  
Ewa Żesławska ◽  
Anna Jakubowska ◽  
Wojciech Nitek
Keyword(s):  
Amino Acids ◽  
Crystal Structures ◽  
Stereoselective Synthesis ◽  
Biologically Active ◽  
Asymmetric Unit ◽  
Conformational Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Natural Amino Acids ◽  
Heterocyclic Moiety

Unnatural cyclic α-amino acids play an important role in the search for biologically active compounds and macromolecules. Enantiomers of natural amino acids with a D configuration are not naturally encoded, but can be chemically synthesized. The crystal structures of two enantiomers obtained by a method of stereoselective synthesis, namely (5R,8S)-8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione, (1), and (5S,8R)-8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione, (2), both C14H21NO4, were determined by X-ray diffraction. Both enantiomers crystallize isostructurally in the space group P21, with one molecule in the asymmetric unit and with the same packing motif. The crystal structures are stabilized by C—H...O hydrogen bonds, resulting in the formation of chains along the [100] and [010] directions. The conformation of the 3,6-dihydro-2H-1,4-oxazin-2-one fragment was compared with other crystal structures possessing this heterocyclic moiety. The comparison showed that the title compounds are not exceptional among structures containing the 3,6-dihydro-2H-1,4-oxazin-2-one fragment. The planar moiety was more frequently observed in derivatives in which this fragment was not condensed with other rings.

scholarly journals Conformational promiscuity in triazolamers derived from quaternary amino acids mimics peptide behaviour

2015 ◽  
Vol 13 (44) ◽  
pp. 10797-10801 ◽  
Author(s):  
Jordi Solà ◽  
Michael Bolte ◽  
Ignacio Alfonso
Keyword(s):  
Amino Acids ◽  
Nmr Spectroscopy ◽  
Click Chemistry ◽  
Secondary Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Natural Peptides

Oligomers made by click chemistry display a duality of secondary structures similar to natural peptides as inferred by NMR spectroscopy and X-ray diffraction experiments.

scholarly journals Preliminary X-ray crystallographic studies of the TIR domain of human Toll-like receptor 6

2014 ◽  
Vol 70 (8) ◽  
pp. 1053-1055 ◽  
Author(s):  
Tae-ho Jang ◽  
Hyun Ho Park
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Immune Response ◽  
Innate Immune ◽  
Toll Like Receptor ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Tir Domain

Toll-like receptor (TLR) proteins have been identified and shown to play a role in the innate immune response. TLR6 associated with TLR2 can recognize diacylated lipoprotein. In this study, the human TLR6 TIR domain corresponding to amino acids 640–796 was overexpressed inEscherichia coliusing engineered C-terminal His tags. The TLR6 TIR domain was then purified to homogeneity and crystallized at 20°C. Finally, X-ray diffraction data were collected to a resolution of 2.2 Å from a crystal belonging to space groupC2, with unit-cell parametersa= 127.60,b= 44.20,c= 75.72 Å, β = 118.89°

scholarly journals Hydrogels formed from Fmoc amino acids

CrystEngComm ◽  
2015 ◽  
Vol 17 (42) ◽  
pp. 8047-8057 ◽  
Author(s):  
Emily R. Draper ◽  
Kyle L. Morris ◽  
Marc A. Little ◽  
Jaclyn Raeburn ◽  
Catherine Colquhoun ◽  
...  
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
X Ray ◽  
Single Crystal Structures

A number of Fmoc amino acids can be effective low molecular weight hydrogelators; we compare single crystal structures to fibre X-ray diffraction data.

Divalent Metal Complexes of 2-Formylphenoxyacetic Acid: The Crystal Structures of 2-Formylphenoxyacetic Acid, and the Isomorphous Cobalt(II) and Zinc(II) 2-Formylphenoxyacetates

1985 ◽  
Vol 38 (9) ◽  
pp. 1381 ◽  
Author(s):  
CHL Kennard ◽  
EJ O'Reilly ◽  
G Smith ◽  
TCW Mak
Keyword(s):  
Metal Complexes ◽  
Crystal Structures ◽  
Divalent Metal ◽  
Carboxyl Groups ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Planar Molecules ◽  
Divalent Metal Complexes ◽  
Monoclinic Cell

The crystal structures of 2-formylphenoxyacetic acid ( ofpaH ), tetraaquabis (2-formylphenoxyacetato)-cobalt(II) (1) and tetraaquabis (2- formylphenoxyacetato )zinc(II) (2) have been determined by X-ray diffraction and refined to residuals R 0.039, 0.058 and 0.045 for 1197, 1178 and 1230 observed reflections respectively. 2-Formylphenoxyacetic acid crystallizes in a monoclinic cell, space group P21/n with a 8.066(2), b 7.375(1), c 14.206(2) Ǻ, β 98.12(1)° and Z 4. The planar molecules form unusual hydrogen-bonded chain polymers (O…O 2.694(3)Ǻ] linked through the carboxyl groups. The complexes (1) and (2) are isomorphous, the comparative cells being a 5.036(1), b 13.463(3), c 15.083(4) Ǻ, β 96.88(2)° for (1), and a 5.044(1), b 13.481(3), c 15.055(4) Ǻ, β 96.95(2)° for (2), with Z 2 and space group P21. The complexes have four waters and two trans-related carboxyl oxygens [mean M-O distances 2.129(5) and 2.117(3) Ǻ respectively] completing almost regular octahedral stereochemistries . The nickel(II) complex [Ni( ofpa )(H2O)4] is probably not isostructural with (1) and (2), and the copper(II) complex is also different, with formula [Cu( ofpa )2(H2O)2].

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