Aldol type reaction of unprotected sugars in methanol
Although aldol condensation of 1,3-dihydroxyacetone with formaldehyde in methanol catalyzed by CaCl2/KOH gave glycero-tetrulose, the reaction catalyzed by Ca(OH)2 preferentially gave 1,3-dihydroxyacetone dimer. The result was explained by the formation of a chelated enolate. This sequence was successfully applied to the stereoselective synthesis of threo-3-pentulose.
Analysis, by g. l. c. - m. s. after isopropylidenation, of the product mixtures obtained by aldol condensation of glycolaldehyde and 1,3-dihydroxy-2-propanone
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Morgenlie, Svein
p. 330 - 334
(2007/10/02)
Kinetics, Catalysis, and Mechanism of the Secondary Reaction in the Final Phase of the Formose Reaction
In the final phase of the formose reaction sugars are formed by the reaction of glycolaldehyde, glyceraldehyde and dihydroxyacetone.The application of high-pressure liquid chromatography allows for the first time to investigate intermediate and final products quantitatively.The results of kinetical investigations allow to suggest a reaction mechanism for the secondary reaction in the final phase of the formose reaction.This mechanism is compared with that of the starting phase and other known mechanisms.From the results metal ion-catalyzed aldol reactions have to be assumed.
Harsch, Guenther,Bauer, Hermann,Voelter, Wolfgang
p. 623 - 635
(2007/10/02)
GAS CHROMATOGRAPHY-MASS SPECTROMETRY OF HEXULOSES AND PENTULOSES AS THEIR O-ISOPROPYLIDENE DERIVATIVES: ANALYSIS OF PRODUCT MIXTURES FROM TRIOSE ALDOL-CONDENSATIONS
Identification and quantitation of hexuloses and pentuloses in mixtures has been achived by gas chromatography-mass spectrometry of their O-isopropylidene derivatives.The method has been applied to product mixtures from triose aldol-condensations.The use of strongly basic anion-exchange resins as catalysts in the aldol condensation gives considerably higher proportions of fructose than when alkali or alkaline-earth hydroxides are applied.