Stereochemistry of complexes of multidentate ligands. II. Geometrical and optical isomers of bis(2,3-diaminopropionato)cobalt(III) ion

ABSTRACT The general change in the connective tissues which occurs in animals with experimentally produced exophthalmos, consists in an increase in the amount of hyaluronic acid, which binds the water in the connective tissue. Many regard this process as a stimulation of the mucinous system in the connective tissues, and consider this an explanation of the phenomenon of exophthalmos. When the experimental animals are injected with thyroxine or thyroid extract, the reaction observed is opposite to that seen following the injection of the anterior lobe of the pituitary gland. In the former case, there is a reduction in the amount of hyaluronic acid and consequently a decrease in the water content in the connective tissues. In the experiments in question, Na-d-thyroxine and Na-l-thyroxine), in crystalline form, were tested for their inhibiting effect on the development of exophthalmos in experimental animals. The animals used were male albino guinea-pigs. An extract of the anterior lobe of the pituitary gland (TSH Organon)) was used to produce exophthalmos. In previous work (Tengroth 1961), it was shown, using an X-ray measuring technique, that d-thyroxine, despite its poor caloric effect, like l-thyroxine had an exophthalmos-inhibiting effect. When comparing the dose-response curves of the exophthalmos-inhibiting properties of both these optical isomers, it appears that d-thyroxine has an inhibiting effect which is significantly greater than that of l-thyroxine. The significance of this observation is discussed.

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Separation and Characterization of Standard Propoxyphene Diastereomers and Their Determination in Pharmaceutical and Illicit Preparations

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/64.4.875 ◽

1981 ◽

Vol 64 (4) ◽

pp. 875-883

Author(s):

Shiv K Soni ◽

Daniel Van Gelder

Keyword(s):

High Pressure ◽

Optical Isomers ◽

Gold Chloride ◽

Melting Points ◽

Eutectic Melting ◽

Racemic Mixtures ◽

The Individual ◽

Isomeric Mixtures ◽

Asymmetric Carbon

Abstract Due to the existence of 2 asymmetric carbon atoms in: the propoxyphene molecule, there are 4 diastereomers: alpha dextro, alpha levo, beta dextro, and beta levo. Only α-d-propoxyphene is included under the federal Controlled Substances Act. Baseline separations of propoxyphene from various incipients (aspirin, caffeine, phenacetin, and acetaminophen) present in pharmaceutical and illicit preparations, and between the alpha and beta diastereomers, were achieved by high pressure liquid chromatography. The column eluant was collected and propoxyphene was extracted. The optical isomers were differentiated and characterized by melting points and by chemical microcrystalline tests. Using hot stage thermomicroscopy, the eutectic melting points of binary isomeric mixtures of propoxyphene bases and salts were found to be depressed about 10° and 15-30°C, respectively, below the individual isomer melting points. The characteristic microcrystals formed with the alpha racemic mixtures by using a glycerin-aqueous gold chloride reagent were not produced by the beta racemic mixtures.

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Rates of Abiotic MnII Oxidation by O2: Influence of Various Multidentate Ligands at High pH

Environmental Science & Technology ◽

10.1021/acs.est.1c01795 ◽

2021 ◽

Author(s):

James J Morgan ◽

Mark A Schlautman ◽

Halka Bilinski

Keyword(s):

Multidentate Ligands ◽

High Ph

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Role of Chiral Configuration in the Photoinduced Interaction of D- and L-Tryptophan with Optical Isomers of Ketoprofen in Linked Systems

International Journal of Molecular Sciences ◽

10.3390/ijms22126198 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6198

Author(s):

Aleksandra A. Ageeva ◽

Ilya M. Magin ◽

Alexander B. Doktorov ◽

Victor F. Plyusnin ◽

Polina S. Kuznetsova ◽

...

Keyword(s):

Amino Acid ◽

Excited States ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Dipole Interaction ◽

The Body ◽

Model Systems ◽

Optical Isomers ◽

Amino Acid Properties ◽

Parkinson’S Diseases

The study of the L- and D-amino acid properties in proteins and peptides has attracted considerable attention in recent years, as the replacement of even one L-amino acid by its D-analogue due to aging of the body is resulted in a number of pathological conditions, including Alzheimer’s and Parkinson’s diseases. A recent trend is using short model systems to study the peculiarities of proteins with D-amino acids. In this report, the comparison of the excited states quenching of L- and D-tryptophan (Trp) in a model donor–acceptor dyad with (R)- and (S)-ketoprofen (KP-Trp) was carried out by photochemically induced dynamic nuclear polarization (CIDNP) and fluorescence spectroscopy. Quenching of the Trp excited states, which occurs via two mechanisms: prevailing resonance energy transfer (RET) and electron transfer (ET), indeed demonstrates some peculiarities for all three studied configurations of the dyad: (R,S)-, (S,R)-, and (S,S)-. Thus, the ET efficiency is identical for (S,R)- and (R,S)-enantiomers, while RET differs by 1.6 times. For (S,S)-, the CIDNP coefficient is almost an order of magnitude greater than for (R,S)- and (S,R)-. To understand the source of this difference, hyperpolarization of (S,S)-and (R,S)- has been calculated using theory involving the electron dipole–dipole interaction in the secular equation.

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