Cobalt(III) Complexes of a Stereospecific Ligand Derived from (S)-Proline

1979 ◽  
Vol 32 (8) ◽  
pp. 1661 ◽  
Author(s):  
T Woon ◽  
MJ O'Conner
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Absolute Configuration ◽  
Cotton Effect ◽  
Low Energy ◽  
Spectral Measurements ◽  
Asymmetric Carbon Atom ◽  
Geometrical Isomers ◽  
Negative Cotton Effect ◽  
Asymmetric Carbon

The quadridentate ligand, (2S,2'S)-1,1'-(ethane-1,2-diyl)bis(pyrrolidine-2-carboxylic acid) dihydrochloride (H2pren,2HCl), has been derived from (S)-proline. The preparations of the cobalt(III) complexes Na [Co(pren)(CO3)],3H2O, [CO(pren)(H2O)2] ClO4,- 2H2O and [Co(pren)(H2O)Cl],1�5H2O are described. All exist as cis-α geometrical isomers. 13C N.M.R. and absorption spectral measurements confirm the cis-α arrangement. The complex cis-α- [Co(pren)(H2O)Cl],1�5H2O rapidly aquates with retention of configuration. The compounds having actual or near C2 symmetry exhibit a strong negative c.d. band under the 1A1g → 1T1g cubic absorption band which is due to the 1A1 →1E tetragonal component, consistent with the Δ absolute configuration imposed by the (S) configuration of the asymmetric carbon atom in the (S)-proline moiety. The o.r.d. spectrum of cis-α-Na [Co(pren)CO3],3H2O in aqueous solution has a negative Cotton effect at low energy as expected for the Δ absolute configuration.

6-Amino-1,11-dimethyl-6,7-dihydro-5H-dibenzo[a,c]cycloheptene-6-carboxylic acid: The first chiral α-amino acid without asymmetric carbon atom

1996 ◽  
Vol 7 (1) ◽  
pp. 231-236 ◽  
Author(s):  
Luděk Ridvan ◽  
Nevine Abdallah ◽  
Roman Holakovský ◽  
Miloš Tichý ◽  
Jiří Závada
Keyword(s):  
Amino Acid ◽  
Carboxylic Acid ◽  
Carbon Atom ◽  
Asymmetric Carbon Atom ◽  
Asymmetric Carbon

The Decomposition of Lasiocarpic and Echimidinic Acids in Hydrochloric Acid

1960 ◽  
Vol 13 (2) ◽  
pp. 269 ◽  
Author(s):  
HC Crowley ◽  
CCJ Culvenor
Keyword(s):  
Carbon Atom ◽  
Hydrochloric Acid ◽  
Absolute Configuration ◽  
Dilute Hydrochloric Acid ◽  
Methoxyl Group ◽  
Asymmetric Carbon Atom ◽  
Asymmetric Carbon

In concentrated hydrochloric acid at 100 �C, lasiocarpic acid is readily decomposed with formation principally of acetaldehyde, dimethylpyruvic acid, and α-keto-ββ-dimethyl-γ-valerolactone. Echimidinic acid is similarly and more rapidly decomposed while trachelanthic and heliotric acids are stable at 100 �C. In dilute hydrochloric acid, lasiocarpic acid is slowly converted into acetaldehyde, acetone, dimethylpyruvic acid, (+)-2-methoxy-4-methylpentan-3-one (IX), 2-methylpent-1-en-3-one (XI), and an unidentified compound. The isolation of IX shows that lasiocarpic and heliotric acids have the same absolute, configuration at the asymmetric carbon atom which bears the methoxyl group.

Studies on the biosynthesis of cholesterol XVIII. The stereospecificity of mevaldate reductase and the biosynthesis of asymmetrically labelled farnesyl pyrophosphate

1966 ◽  
Vol 163 (993) ◽  
pp. 465-491 ◽  
Keyword(s):  
Carbon Atom ◽  
Absolute Configuration ◽  
Farnesyl Pyrophosphate ◽  
Asymmetric Carbon Atom ◽  
Isotopic Label ◽  
Asymmetric Carbon

It is demonstrated that mevaldate reductase transfers hydrogen stereospecifically from the ‘Aʼ-side of NADH or NADPH to substrate. When 4 R -[ 3 H 1 ]NADH, or NADPH, is used for the reduction of mevaldate the resulting [5. 3 H 1 ]mevalonate is stereospecifically labelled at C-5 with an absolute configuration of R . Mevaldate reductase shows no stereospecificity for the asymmetric carbon atom, C-3, in mevaldate: the product of the reduction of 3 RS -mevaldate is 3 RS -mevalonate. 5 R -[5. 3 H 1 ]- and 5 R -[5-D 1 ]mevalonate have been prepared and used for the synthesis of 1 R -[1,5,9. 3 H 3 ]- and 1 R -[1,5,9-D 3 ]farnesyl pyrophosphate and squalene. It is shown that when squalene is synthesized from such farnesyl pyrophosphate all the isotopic label appears in the squalene without loss. The implications of the last observations are discussed in the light of previous results.

Evaluation of Different Synthetic Routes to (2R,3R)-3-Hydroxymethyl-2-(4-hydroxy- 3-methoxyphenyl)-1,4-Benzodioxane-6-Carbaldehyde

2020 ◽  
Vol 23 (26) ◽  
pp. 2960-2968
Author(s):  
Renáta Kertiné Ferenczi ◽  
Tünde-Zita Illyés ◽  
Sándor Balázs Király ◽  
Gyula Hoffka ◽  
László Szilágyi ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Stereoselective Synthesis ◽  
Cotton Effect ◽  
Enantioselective Synthesis ◽  
Aryl Group ◽  
Target Molecule ◽  
Synthetic Routes ◽  
The Absolute

The reported enantioselective synthesis for the preparation of (+)-(2R,3R)-2-(4- hydroxy-3-methoxyphenyl)-3-hydroxymethyl-1,4-benzodioxane-6-carbaldehyde, precursor for the stereoselective synthesis of bioactive flavanolignans, could not be reproduced. Thus, the target molecule was prepared via the synthesis and separation of diastereomeric O-glucosides. TDDFT-ECD calculations and the 1,4-benzodioxane helicity rule were utilized to determine the absolute configuration. ECD calculations also confirmed that the 1Lb Cotton effect is governed by the helicity of the heteroring, while the higher-energy ECD transitions reflect mainly the orientation of the equatorial C-2 aryl group.

Outer-sphere interaction of (S)-asparagine and (S)-glutamine with [Co(NH3)6]3+ ion and its possible role in ligand substitution

1987 ◽  
Vol 52 (10) ◽  
pp. 2457-2459
Author(s):  
František Jursík
Keyword(s):  
Amino Acids ◽  
Transition Region ◽  
Alkaline Medium ◽  
Optical Activity ◽  
Substitution Reaction ◽  
Outer Sphere ◽  
Ligand Substitution ◽  
Cotton Effect ◽  
Negative Cotton Effect

Optical activity of the achiral cation [Co(NH3)6]3+ is induced both by (S)-AsnONa and (S)-GlnONa, as shown by a negative Cotton effect in the 1A1g → 1T1g transition region. An outer-sphere interaction by three-point attachment of the amides can explain the fact that substitution reaction of [Co(NH3)6]3+ with the mentioned amides in an alkaline medium is unusually slow as compared with other amino acids.

scholarly journals Electrochemiluminescence Study of Europium (III) Complex with Coumarin3-Carboxylic Acid

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Stefan Lis ◽  
Krzysztof Staninski ◽  
Tomasz Grzyb
Keyword(s):  
Aqueous Solution ◽  
Spectral Analysis ◽  
Energy Transfer ◽  
Solid State ◽  
Carboxylic Acid ◽  
Elemental Analysis ◽  
Aluminium Electrode ◽  
The Eu

The europium (III) complex of coumarin-3-carboxylic acid (C3CA) has been prepared and characterized on the basis of elemental analysis, IR, and emission (photoluminescence and electrochemiluminescence) spectroscopy. The synthesised complex having a formula Eu was photophysically characterized in solution and in the solid state. Electrochemiluminescence, ECL, of the system containing the Eu(III)/C3CA complex was studied using an oxide-covered aluminium electrode. The goal of these studies was to show the possibility of the use of electrochemical excitation of the Eu(III) ion in aqueous solution for emission generation. The generated ECL emission was very weak, and therefore its measurements and spectral analysis were carried out with the use of cut-off filters method. The studies proved a predominate role of the ligand-to-metal energy transfer (LMET) in the generated ECL.

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