The synthesis and stereochemistry of the ternary cobalt(III) complex with a stereospecific ligand derived from (S)-leucine

1986 ◽  
Vol 51 (2) ◽  
pp. 318-326 ◽  
Author(s):  
Milan Strašák ◽  
Pavol Novomeský
Keyword(s):  
Ir Spectroscopy ◽  
Aqueous Medium ◽  
Absorption Spectroscopy ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Methyl Groups ◽  
Electron Absorption Spectroscopy ◽  
Electron Absorption ◽  
C Nmr

A new stereospecific ligand, ethylenediamine-N,N'-di(S)-α-isocapronic acid, was synthesized by condensation of (S)-leucine with 1,2-dibromoethane in alkaline aqueous medium. It follows from the 1H and 13C NMR spectra that the terminal methyl groups are chemically and magnetically nonequivalent. Of the four theoretically possible isomers of the ternary cobalt (III) complex with ethylenediamine, separation on catex yielded only one, whose absolute configuration was determined by a combination of 1H and 13C NMR, electron absorption spectroscopy and CD and IR spectroscopy.

Δ-Sym-cis and Δ-unsym-cis-carbonato-(2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato)cabaltate(III) isomers

1987 ◽  
Vol 52 (6) ◽  
pp. 1488-1493 ◽  
Author(s):  
František Jursík ◽  
Samir Abdel-Moez
Keyword(s):  
Acid Hydrolysis ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Tetradentate Ligand ◽  
Steric Crowding ◽  
The Absolute ◽  
Kinetic Effects ◽  
Hydrolysis Of ◽  
C Nmr

The tetradentate ligand (2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato) (eddval) is coordinated in the [Co(eddval)CO3]- anion to give 88% of Δ-sym-cis and 12% of Δ-unsym-cis isomers. The stereospecific formation of the Δ-sym-cis isomer is explained by steric crowding in the Λ-sym-cis isomer. The predominance of the sym-cis isomer indicates that the synthesis is also influenced by kinetic effects. These are particularly pronounced in the case of the Δ-unsym-cis isomer which for steric reasons is thermodynamically less stable than the Λ-unsym-cis isomer. The secondary nitrogen atoms in the Δ-sym-cis isomer are of the R configuration whereas in the Δ-unsym-cis isomer they have configuration R and S. The absolute configuration of the isomers has been determined from their absorption, CD, 1H and 13C NMR spectra. Acid hydrolysis of Δ-sym-cis-[Co(eddval)CO3]- proceeds with retention of configuration to give the Δ-[Co(eddval)(H2O)2]+ isomer.

Assignment of Nitrogen Stereochemistry of Agroclavine and Elymoclavine 6-N-Oxides

1995 ◽  
Vol 60 (12) ◽  
pp. 2165-2169 ◽  
Author(s):  
Vladimír Křen ◽  
Jan Němeček ◽  
Věra Přikrylová
Keyword(s):  
Hydrogen Peroxide ◽  
Absolute Configuration ◽  
Molecular Modelling ◽  
Nmr Spectra ◽  
Peroxide Oxidation ◽  
Hydrogen Peroxide Oxidation ◽  
C Nmr

Both possible 6-N-oxides of agroclavine (I) and elymoclavine (II) were prepared by hydrogen peroxide oxidation. Their 1H and 13C NMR spectra were assigned and the conformation of the D ring (half-chair) was determined. Absolute configuration at 6-N was established by NMR and molecular modelling.

scholarly journals Kernresonanzspektroskopische Untersuchungen an t-Butyl-phenyl-phosphinsäure-(—)-menthylester, II [1]1H-, 13C-und 31P-NMR-Analyse der absoluten Konfiguration am Phosphoratom / NMR Spectroscopic Investigations on t-Butyl-phenyl-phosphinic Acid(—)-Menthyl Ester, II [1] 1H, 13C and 31P NMR Analysis of Absolute Configuration at the Phosphorus Center

1980 ◽  
Vol 35 (10) ◽  
pp. 1182-1190 ◽  
Author(s):  
Gerhard Hägele ◽  
Detlef Wendisch ◽  
Reiner Luckenbach ◽  
Hans-H. Bechtolsheimer
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Double Resonance ◽  
Phosphinic Acid ◽  
Nmr Analysis ◽  
Spectroscopic Investigations ◽  
Phosphinic Acids ◽  
13C And 31P Nmr ◽  
C Nmr

Abstract(-)-Menthol, Diastereomeric Menthylesters of Phosphinic Acids, 31P NMR Spectra, 13C NMR Spectra, Double Resonance(-)-Menthol and diastereomeric (-)-menthyl esters of t-butyl-phenyl-phosphinic acid are investigated by means of 1H, 13C and 31P NMR at 2.1 and 8.4. Tesla double resonance experiments are described.

Preparation of C(18)-empiric 20,29,30-trinorlupane derivatives. 1H, 13C NMR and mass spectra

1986 ◽  
Vol 51 (3) ◽  
pp. 621-635 ◽  
Author(s):  
Václav Křeček ◽  
Jiří Protiva ◽  
Miloš Buděšínský ◽  
Eva Klinotová ◽  
Alois Vystrčil
Keyword(s):  
Nitrous Acid ◽  
Mass Spectra ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Allylic Oxidation ◽  
Hydroxyl Group ◽  
Methyl Groups ◽  
Unsaturated Ketone ◽  
H Nmr ◽  
C Nmr

Reaction of amide I with nitrous acid gave the olefins II, III and IV. On allylic oxidation of olefin IV α,β-unsaturated ketone V is formed from which olefins VIII and IX were prepared by a sequence of further reactions. Addition of hydrogen to the double bond of olefin IV and α,β-unsaturated ketone V takes place on catalytic hydrogenation from the β-side and leads to derivatives with cis-annellated rings D/E. This made the preparation of hydrocarbons VI and VII epimeric on C(18) possible, which represent reference compounds for the study of the effect of substituents on the chemical shifts of the methyl groups and the saturated carbon atoms of 18αH and 18βH-lupane derivatives. The configuration of the hydroxyl group in epimers XI and XII were derived from 1H NMR spectra. Deuteration of olefins III, IV and IX gave deuteriohydrocarbons XVI to XVIII. The 1H, 13C NMR and mass spectra of the substances prepared are discussed.

29Si and 13C NMR spectra of some alkyldiphenylchlorosilanes, alkyldiphenylsilanoles and bis(alkyldiphenylsilyl)chromates

1982 ◽  
Vol 47 (2) ◽  
pp. 603-612 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
Karel Handlíř ◽  
Jaroslav Holeček ◽  
Milan Nádvorník
Keyword(s):  
Electron Acceptor ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Methyl Groups ◽  
Induction Effect ◽  
13C Nmr Spectra ◽  
Electronegative Substituent ◽  
Good Linear Correlation ◽  
C Nmr

29Si and 13C NMR spectra of alkyldiphenylchlorosilanes, alkyldiphenylsilanoles, and bis(alkyldiphenylsilyl)chromates (C6H5)2Si(R)X have been studied. The chemical shifts δ(29Si) are most affected by nature of the electronegative substituent X, i.e. Cl, OH or CrO3OSi(R). (C6H5)2. The δ(29Si) shifts due to effects of the substituents R can be correlated successfully with values of the Taft constants σ. Slopes of the correlation dependences have negative signs for all the groups of the studied compounds (increasing electron-acceptor ability of substituent R causes upfield shifts of δ(29Si), and their values decrease with increasing electronegativity of the substituent X (sensitivity of the δ(29Si) shifts due to sustituent R increases with increasing electronegativity of the substituent X). Methyl groups at γ-position of the chain of substituent R cause a diamagnetic shift of δ(29Si) by 0.6 to 3.3 ppm. The δ(13C) shifts depend little on nature of the substituent X. Chemical shifts δ(13C) of carbon atoms at α-, β-, and γ-positions of the substituent R with respect to silicon show a good linear correlation with the δ(13C) shifts of the corresponding carbon atoms in aliphatic hydrocarbons CH3R. Slopes of the correlation dependences of all the groups of studied compounds are close to 1, the intercepts for α- and β-positions are negative because of induction effect. Positive value of the intercepts for γ-positions reflects the influence of sterical γ-effect.

CD of primary amines and 1- or 3-substituted tetrahydroisoquinolines in presence of [Rh2(O2CCH3)4]

1991 ◽  
Vol 56 (5) ◽  
pp. 954-965 ◽  
Author(s):  
Wolfgang Diener ◽  
Jadwiga Frelek ◽  
Günter Snatzke
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Pure Form ◽  
Primary Amines ◽  
Methyl Groups ◽  
Optically Pure

The syntheses of (S)-(-)-1,2-dimethyl-1,2,3,4-tetrahydroisoquinoline (IX) and (S)-(+)-2,3-dimethyl-1,2,3,4-tetrahydroisoquinoline (XVI) [ via (S)-1-benzoyl-N-ethoxycarbonyl ethylamine (XI)] in optically pure form and with known absolute configuration is described. The CD and NMR spectra of these compounds and of most of their intermediates are given, and from these data could be deduced, that the N-methyl groups of the two bases IX and XVI adopt different conformations in solution, but the same (viz. axial) in their complexes with [Rh2(OAc)4].

Study of Amino-Imino Tautomerism in Derivatives of 2-, 4- and 6-Aminonicotinic Acid

1994 ◽  
Vol 59 (9) ◽  
pp. 2057-2068 ◽  
Author(s):  
Svatava Smrčková ◽  
Kristina Juricová ◽  
Viktor Prutianov
Keyword(s):  
Ir Spectroscopy ◽  
Hydrogen Bonds ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Amino Derivative ◽  
Ionic Character ◽  
H Nmr ◽  
Amino Derivatives ◽  
Derivatives Of ◽  
C Nmr

13C NMR spectra of p-nitrobenzoyl 2-, 4-, and 6-aminopyridine-3-carboxylates, their hydrochlorides, trifluoroacetates and 1-benzyl derivatives were studied. As found from the chemical shifts of pyridine carbon atoms C-2, C-4 and C-6, the free bases exist in the amino form whereas hydrochlorides and 1-substituted pyridinium derivatives in the imino form. Trifluoroacetates of the 2- and 6-amino derivatives have structure similar to that of amidiniumcarboxylates (parallel hydrogen bonds and partially ionic character) whereas trifluoroacetate of the 4-amino derivative is structurally close to the corresponding hydrochloride. The found structures were confirmed by 1H NMR and IR spectroscopy.

scholarly journals Configurational Study of an Aporphine Alkaloid from Annona purpurea

2018 ◽  
Vol 13 (7) ◽  
pp. 1934578X1801300 ◽  
Author(s):  
Julio C. Ontiveros-Rodríguez ◽  
Eleuterio Burgueño-Tapia ◽  
Javier Porras-Ramírez ◽  
Pedro Joseph-Nathan ◽  
L. Gerardo Zepeda
Keyword(s):  
Nitrogen Atom ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Optical Rotation ◽  
Vibrational Circular Dichroism ◽  
Aporphine Alkaloid ◽  
Stereogenic Center ◽  
First Time ◽  
C Nmr

Purpureine (1), norpurpureine (2), and 3-hydroxyglaucine (4) were isolated from the leaves of Annona purpurea. A vibrational circular dichroism study for the absolute configuration determination of 1 provides evidence for the mutually dependent atropisomerism, local chirality of the sole stereogenic center, and the geometry of the tetrahedral nitrogen atom in aporphine alkaloids. The observed change in the optical rotation sign between 2 and its hydrochloride 3 might explain why this compound has been reported as dextrorotatory and levorotatory from the same botanical source. Furthermore, 1H and 13C NMR spectra of 1, 2 and 4 were fully assigned for the first time.

Hydrolyse des dérivés de cyclopropylidène-3 propyle. Structure et stéréochimie des alcools précurseurs et des produits résultant de l'hydrolyse

1981 ◽  
Vol 59 (7) ◽  
pp. 1089-1095 ◽  
Author(s):  
Robert Faure ◽  
Gilbert Leandri ◽  
Alain Meou
Keyword(s):  
Ir Spectroscopy ◽  
Nmr Spectra ◽  
Molecular Conformation ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Hydrolysis Products ◽  
Hydrolysis Of ◽  
C Nmr

The 13C nmr spectra of 14 β-cyclopropylidenic alcohols 1 have been determined:[Formula: see text]All the chemical shifts were assigned and the substituent effects are discussed as a function of molecular conformation. The stereochemistry of two diastereoisomers of alcohols 1e (R1 = R3 = H; R2 = R4 = CH3) and 1k (R3 = H; R1 = R2 = R4 = CH3) was established from ir spectroscopy and 1H nmr results.The 13C nmr spectra of products arising from hydrolysis of 3-cyclopropylidene propanol 1a and 4-cyclopropylidene 2-butanol 1b tosylates have been also recorded. The analysis of these data enables us to establish unambiguously the structure and the stereochemistry of the hydrolysis products.

The molecular conformations of 8,11-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin and 4,4-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin

1985 ◽  
Vol 63 (8) ◽  
pp. 2185-2191 ◽  
Author(s):  
A. Lachapelle ◽  
M. St-Jacques
Keyword(s):  
Low Temperature ◽  
Ir Spectroscopy ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Substituent Effects ◽  
Methyl Groups ◽  
Spectroscopy Analysis ◽  
Molecular Conformations ◽  
Conformational Properties ◽  
Stretching Vibrations

The conformational properties of 8,11-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (5) and of 4,4-dimethyl-5,6-benzo-2-oxo-1,3,2-dioxathiepin (6) have been investigated using 1H and 13C dnmr as well as ir spectroscopy. Analysis of low temperature nmr spectra (down to −148 °C) and of S=O stretching vibrations in room temperature ir spectra indicates that the most stable conformations detected for solutions in CHF2Cl/CD2Cl2 (80:20) are TB (83%) and C-a (17%) for 5 and only the TB 7 for 6. Substituent effects of methyl groups at the peri and the benzylic positions on the conformational properties of the seven-membered sulfites are discussed.

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