Aldehydes, phytochemical reduction

Phytochemical Reduction of Keto Acids and Keto Aldehydes. 85... 

Phytochemical Reduction of Aromatic and Aliphatic-Aromatic Aldehydes... 

The possibility of hydrogenating halogenated aldehydes and ketones by means of phytochemical reduction was tested as early as 1913 the successful results in this field clearly demonstrate the importance of this method. Lintner and Ltters found that chloral hydrate can be converted to trichloroethyl alcohol. This transformation takes place so easily that, according to Willstatter and Duisberg, it can be used under favorable experimental conditions as a convenient method for the preparation of the halogenated alcohol. The tribromoethyl alcohol may be prepared in an analogous manner. 

Ketones, in contrast to aldehydes, occur frequently in plants. A phytochemical reduction of the keto group has been shown in aliphatic, aromatic s and cyclic ketones although it takes longer and is less complete than in the case of aldehydes. (For the theory of this transformation see Neuberg and Gorr. )... 

After phytochemical reduction was noted in the case of aldehydes and ketones, interest arose in the behavior of fermenting cells toward compounds containing several carbonyl groups per molecule, such as diketones and quinones. This class deserves special consideration because the simplest representative, diacetyl, as well as its products of reduction, acetylmethylcarbinol (3-hydroxybutanone) and 2,3-butylene glycol, are connected with the metabolism of numerous cells quinones also are biologically important. 

When a racemic substance is hydrogenated or when the reduction leads to the production of centers of asymmetry, the phytochemical reduction will take at first a completely or partially asymmetric course. Examples of such asymmetric reactions are the conversions of pure racemic valeraldehyde, acetaldol, furoin and furil, diacetyl and acetyl-methylcarbinol to optically active alcohols. Occasionally meso forms also arise, as for example in the case off glycols (p. 84). The reasons for the stereochemical specificity of these reactions have not been clarified. This type of phenomenon has frequently been observed in the related intramolecular dismutation of keto aldehydes, especially if enzyme materials of differing origins are used. 

The formation of mercaptan is doubly important because of its relation to phytochemical reduction processes. The reaction is analogous to the formation of ordinary alcohols from aldehydes and it also indicates how the plant is capable of synthesizing intensely odorous substances from aldehydes and hydrogen sulfide in a simple manner. The isolation... 

The connection of the aromatic mono-, di- and tri-nitro compounds with phytochemical reduction follows from their activating action in alcoholic fermentation, known for a quarter century.The same applies equally to the excellent activating effect of cinnamic aldehyde its behavior during phytochemical eduction is described on pages 79 and 105. 

The reduction of butyric acid seems to proceed by way of n-butyr-aldehyde. The phytochemical reduction to butyl alcohol previously demonstrated for yeast (see p. 78) has also been carried out with bacteria. Regarding the reduction of butyric acid to n-butanol, papers of Bernhauer and coworkers, Kluyver and Donker, Stiles, Peterson and Fred, Janke and Siedler and Wood, Brown and Workman should be consulted. Peynaud ascribes also to wine yeast the ability to... 

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