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Chapter
Carotenoids: Introduction
As is well known, the carotenoid pigments belong to the class of polyenes and represent the most unsaturated mass products of biosynthesis. Several carotenoid pigments are extremely widespread in the vegetable...
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Chapter
Some Properties of cis Carotenoids
An all-trans carotenoid, because of its nearly coplanar chromophore and perfect resonance, is generally expected to surpass in stability its cis isomers. Nevertheless it should be pointed out that simple characte...
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Preparation of cis Carotenoids by Direct Rearrangement of the All-trans Form
Cis carotenoids have been obtained by stereo isomerization of all-trans pigments, by total synthesis, and by isolation from plants or animals.
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Chapter
Cis-trans Isomerism and Provitamin A Effect of Carotenoids
The chemical and biological relationships between carotene and vitamin A have been established by the classical investigations of Steenbock (412), Moore (320), Euler (111), Karrer (112), and others. It is now wel...
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Naturally Occurring cis and Polycis Carotenoids
As we have seen, the overwhelming majority of plant carotenoids possess the all-trans configuration. To what extent the more energy-rich cis carotenoids appear in plants and animals is a question of biological an...
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Chapter
I-Monoaryl-polyenes
The stereo chemical relationships in the extended class of mono-aryl-polyenes will be illustrated by two very different substances: I-Phenylbutadiene is a lower molecular weight, volatile liquid; hence, the separ...
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Cumulenes with Aromatic Terminal Groups
As is well known, the cumulenes (in German, “Kumulene”) possess n double bonds attached to n + I carbon atoms, the simplest representatives being allenes (propadienes) C=C=C and butatrienes C=C=C=C. They can be c...
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Number and Types of cis Carotenoids. Steric Hindrance
As mentioned, the carotenoids and related multiconjugated systems constitute a unique case among low-molecular weight substances because of the great number of possible geometrical isomers.
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Lower-molecular Weight Carotenoid-carboxylic Acids: Bixin and Crocetin
The carbon skeletons of these stereo chemically important pigments are identical with the middle section of the β-carotene molecule but the chromophore is terminated by conjugated carboxyl groups. Hence, it can b...
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Chapter
Preparation of cis Carotenoids by Total Synthesis
The most brilliant achievement in polyene chemistry during the last decade has been the total synthesis of certain naturally occurring carotenoids and of some analogs and homologs that have not yet been found ...
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Some General Remarks on Configurational Assignments
As we have seen, the spectral curve of a carotenoid is a function of the molecular shape and hence of the spatial configuration. Were the rules that govern this relationship fully known, it would be easy to as...
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Chapter
Polyene Azines
It was interesting to extend the study of diarylpolyenes to this symmetrical series that is characterized by a centrally located =N—N= group. Although the lowest homolog, benzalazine (n = o) has given negative re...
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Configurational Assignments in Certain Stereoisomeric Sets
In this Chapter an attempt will be made to summarize our knowledge concerning cis configurations proposed on the basis of stereo isomerization experiments and to coordinate them with the information gained by tot...
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Chapter
Bibliography
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Chapter
Cis-trans Isomerism and UV Spectra
The intense color of carotenoids is caused by the strong extinction in the region, 400–500 mμ, where the spectral curve shows a massive band. If the latter exhibits vibrational fine structure, in most instances t...
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Chapter
Vitamins A and Retinenes
As is well known, the vitamins A and retinenes are lower isoprenologs of the monocyclic carotenoid pigments; their molecules contain 20 carbon atoms instead of 40. As a special feature they carry functional gr...
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α,ω-Diphenylpolyenes and Related Compounds
Representatives of this series, up to n = 8, have been synthesized by Kuhn and Winterstein long ago (269). In each set they obtained the same end product, even when ten different routes had been followed. Althoug...
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