Lobry de Bruyn-Van Ekenstein reaction

The synthesis of D-psicose as a colorless sirup ([< ]% + 3.1° in water) by Steiger and Reichstein13 may be regarded as the first authentic preparation of this ketohexose. The Kiliani-Fischer cyanohydrin synthesis furnished D-allonic lactone (VII) from D-ribose. This lactone, on reduction with sodium amalgam, gave D-allose (VIII) which was transformed into D-psicose (I) by refluxing with pyridine. Pyridine had been introduced into the Lobry de Bruyn-Van Ekenstein reaction by Fischer, Danilov and their coworkers.13 ... 

Reactions with bases in basic medium, reducing sugars undergo isomerization reactions through enedioi intermediates (Lobry De Bruyn-Van Ekenstein reaction) so glucose is partially converted to fructose and mannose a number of by-products is also produced. 

Chemists usually learn about reactions according to fiinctional groups for example, How can I make an aldehyde and what reactions are known for aldehydes " This is clearly not a very good starting point for classifying reactions. The poor state of affairs in the definition of reaction types is further quite vividly illustrated by the fact that many chemical reactions are identified by being named after their inventor Diels-Alder reaction, Michael addition, Lobry-de Bruyn-van Ekenstein rear-... 

MPa H2. To suppress the isomerization of D-glucose to D-mannose and D-fructose (Lobry de Bruyn-van Ekenstein transformation) (Scheme 5.2) and the Cannizzaro reaction, which were both promoted in an alkaline medium, the pH value was maintained between 5.5 and 6.5. Under the conditions that were optimized to minimize the side reactions, the formation of gluconic acid and mannitol was reduced to less than 1% each at 99.5-99.6% conversion, while with a normal nonpromoted Raney Ni 1.5-2.1% of gluconic acid and 1.3-1.9% of mannitol were formed at 99.5-99.7% conversion. 

This reaction is related to the Lobry de Bruyn-van Ekenstein transformation of aldoses involving the rearrangement of A-alkylamino-D-glucopyranosides into 1-alkylamino-l-deoxy-D-fructoses. ... 

This reaction was first reported by Lobry de Bruyn in 1895, and explored extensively by Lobry de Bruyn and Alberda van Ekenstein. It is the reciprocal interconversion of carbohydrates into their isomers in an alkaline solution through the enediolic intermediate. The name of reaction given here is probably the only one time the full name of the people who discovered such reaction. It is known as the Lobry de Bruyn-Alberda van Ekenstein rearrangement, Lobry de Bruyn-Alberda van Ekenstein transformation, Lobry de Bruyn-Albreda van Ekenstein C-2 epimerization, or Lobry de Bruyn-van Ekenstein transformation. ... 

Lobry de Bruyn-van Ekenstein Transformation Loftier (see Hofmann-Loffler-Freytag Reaction)... 

Angyal SJ (2001) The Lobry de Bruyn-Alberda van Ekenstein Transformation and Related Reactions. 215 1-14... 

Albrecht M (2004) Supramolecular Templating in the Formation of Helicates. 248 105-139 Ando T, Inomata S-I, Yamamoto M (2004) Lepidopteran Sex Pheromones. 239 51-96 Angyal SJ (2001) The Lobry de Bruyn-Alberda van Ekenstein Transformation and Related Reactions. 215 1-14... 

Lobry de Bruyn-Alberda van Ekenstein reaction, 4 712 Lobsters, aquaculture, 3 189 Local chain conformation, HDPE, 20 162 Local emergency planning committee (LEPC), 21 589... 

Aldoses generally undergo benzilic acid-type rearrangements to produce saccharinic acids, as well as reverse aldol (retro-aldol) reactions with j3-elimination, to afford a-dicarbonyl compounds. The products of these reactions are in considerable evidence at elevated temperatures. The conversions of ketoses and alduronic acids, however, are also of definite interest and will be emphasized as well. Furthermore, aldoses undergo anomerization and aldose-ketose isomerization (the Lobry de Bruyn-Alberda van Ekenstein transformation ) in aqueous base. However, both of these isomerizations are more appropriately studied at room temperature, and will be considered only in the context of other mechanisms. 

The reaction of carbohydrates in alkaline or acidic aqueous solutions results in a myriad of products, many of which have been recognized for well over a century. The number of identified products has greatly increased in recent years, owing to the development of sophisticated techniques for separation and identification. With the exception of anhydro sugars and oligosaccharides, found as concentration-dependent, equilibrium constituents (reversion products) in acidic solutions, all of the products result from reactions of intermediates present in the Lobry de Bruyn-Alberda van Ekenstein transformation. 

The products obtained by the reaction of sugars with aqueous ammonia for a short time at low temperature, in the absence of catalysts (see Table I) are simply those obtained by the action of alkali on the sugars. The reaction is known as the Lobry de Bruyn-Alberda van Ekenstein transformation87 after the chemists who dis-... 

The complex reactions of alkalies with reducing sugars have been described extensively. The origin of the initial products that are obtained is usually explained by the classical Lobry de Bruyn and Alberda van Ekenstein transformation,80 in which an enediol (XLVI) is proposed as the key intermediate. In recent studies Sowden and Schaffer61 used D-glucose-l-C14, D-fructose-l-C14, and D-glucose in D20 to... 

The main reactions are 1,2-enolisation (Lobry de Bruyn-Alberda van Ekenstein rearrangement, cf. Amadori rearrangement), dehydration to furfurals, and fission (see ref. 563). 

Lobry de Bruyn-Alberta van Ekenstein reaction) A base-catalyzed tautomerization that interconverts aldoses and ketoses with an enediol as an intermediate. This enolization also epimer-izes C2 and other carbon atoms, (p. 1115)... 

The Amadori rearrangement has some features of the Lobry de Bruyn-Alberda van Ekenstein transformation, as can be seen from the ammono analogy to sugar enolization formulated in Part 2 of this Section. Both reactions occur in basic media, and each doubtless involves 1,2-enolization of the sugar. However, the Amadori rearrangement proceeds by acceptance of a proton from the acid catalyst, whereas the Lobry de Bruyn Alberda van Ekenstein transformation proceeds by delivery of a proton to the base catalyst. Aside from what may be argued as to the enolization mechanism, there are other important differences. 

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