ChemInform Abstract: Photosensitized (4 + 2) Cyclodimerizations of Aromatic Retinoids.

Pfoertner, Karl-Heinz; Englert, Gerhard; Schoenholzer, P.

doi:10.1002/chin.198826312

Cited by 2 publications

(4 citation statements)

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“…From the literature (Mousseron-Canet et al, 1968;Burger and Garbers, 1973;Pfoertner et al, 1988) it is known that different kitol isomers do exist, which can be formed from all-E and Z-isomers of the retinyl esters. The exact mechanism of kitol formation with respect to isomer distribution and exact structure determination of the reaction products will not be investigated in this study.…”

Section: Resultsmentioning

confidence: 99%

“…Retinol and retinyl ester molecules are chemically reacting with one another, forming so-called kitols and kitol esters, that is, dimers of vitamin A derivatives (Giannotti et al, 1966;Mousseron-Canet et al, 1968;Burger and Garbers, 1973;Das, 1974;Pfoertner et al, 1988). Natural kitol has first been discovered in whale liver oil.…”

Section: Introductionmentioning

confidence: 99%

“…Natural kitol has first been discovered in whale liver oil. Synthetically, these dimers can be formed in a thermally induced Diels-Alder reaction (Giannotti et al, 1966;Mousseron-Canet et al, 1968;Burger and Garbers, 1973) and in photochemically induced reactions (Mousseron-Canet et al, 1968;Das, 1974;Pfoertner et al, 1988). Under oxygen-free conditions, the kitol formation or vitamin A degradation will be much faster if the samples are illuminated.…”

Section: Introductionmentioning

confidence: 99%

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Use of Microcalorimetry in Monitoring Stability Studies. Example: Vitamin A Esters

Runge¹,

Heger²

1999

J. Agric. Food Chem.

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Vitamin A is very sensitive to chemical degradation caused by oxygen, light, heat, and other stress factors. If light and oxygen are excluded, the dominant degradation reaction for vitamin A derivatives is heat-induced formation of kitols, that is, dimers or higher oligomers. In this study vitamin A esters were used as model systems to evaluate microcalorimetry as a tool for monitoring the stability of heat sensitive substances. To obtain more knowledge about the model reaction, analytical investigations (supercritical fluid chromatography) were also performed. Because analytical and microcalorimetry data were consistent, a quantitative description of the kinetics and thermodynamics of the kitol formation reaction could be obtained. Aside from the academic motivation, this is important for practical purposes such as shelf life stability of vitamin A in feed, food, and pharmaceutical products. The vitamin A stability of a given sample can easily be predicted from the initial heat flow in a simple microcalorimetry experiment. Compared to conventional stability tests, this offers savings of money and time.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use of Microcalorimetry in Monitoring Stability Studies. Example: Vitamin A Esters

Runge¹,

Heger²

1999

J. Agric. Food Chem.

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“…A simple way in which evolution could substitute chemical for light would be to replace the quantum of light with a monoene, if the monoene could react with a retinoid. In fact, retinoids undergo both thermal-and photo-promoted Diels-Alder reactions, and are capable of behaving as 2-or as 4-electron donating species in both cases (Shealy et al, 1996;Burger and Garbers, 1973;Vogt et al, 1991;Pfoertner et al, 1987Pfoertner et al, , 1988. Pericyclic reactions such as the Diels-Alder reaction are easily generalized.…”

Section: Introductionmentioning

confidence: 99%

Protein-Assisted Pericyclic Reactions: An Alternate Hypothesis for the Action of Quantal Receptors

Radding

Romo

Phillips

1999

Biophysical Journal

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The rules for allowable pericyclic reactions indicate that the photoisomerizations of retinals in rhodopsins can be formally analogous to thermally promoted Diels-Alder condensations of monoenes with retinols. With little change in the seven-transmembrane helical environment these latter reactions could mimic the retinal isomerization while providing highly sensitive chemical reception. In this way archaic progenitors of G-protein-coupled chemical quantal receptors such as those for pheromones might have been evolutionarily plagiarized from the photon quantal receptor, rhodopsin, or vice versa. We investigated whether the known structure of bacteriorhodopsin exhibited any similarity in its active site with those of the two known antibody catalysts of Diels-Alder reactions and that of the photoactive yellow protein. A remarkable three-dimensional motif of aromatic side chains emerged in all four proteins despite the drastic differences in backbone structure. Molecular orbital calculations supported the possibility of transient pericyclic reactions as part of the isomerization-signal transduction mechanisms in both bacteriorhodopsin and the photoactive yellow protein. It appears that reactions in all four of the proteins investigated may be biological analogs of the organic chemists' chiral auxiliary-aided Diels-Alder reactions. Thus the light receptor and the chemical receptor subfamilies of the heptahelical receptor family may have been unified at one time by underlying pericyclic chemistry.

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ChemInform Abstract: Photosensitized (4 + 2) Cyclodimerizations of Aromatic Retinoids.

Cited by 2 publications

References 1 publication

Use of Microcalorimetry in Monitoring Stability Studies. Example: Vitamin A Esters

Use of Microcalorimetry in Monitoring Stability Studies. Example: Vitamin A Esters

Protein-Assisted Pericyclic Reactions: An Alternate Hypothesis for the Action of Quantal Receptors

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