In
carbohydrate chemistry, the Lobry de Bruyn–Van Ekenstein transformation also known as the Lobry de Bruyn–Alberda van Ekenstein transformation is the
base or acid
catalyzed transformation of an aldose into the ketose isomer or vice versa, with a
tautomericenediol as
reaction intermediate. Ketoses may be transformed into 3-ketoses, etcetera. The enediol is also an intermediate for the
epimerization of an
aldose or
ketose.
[1][2]
The following scheme describes the interconversion between an aldose and a ketose, where R is any
organic residue.
The equilibrium or the reactant to product ratio depends on
concentration,
solvent,
pH and
temperature. At equilibrium the aldose and ketose form a mixture which in the case of the glyceraldehyde and dihydroxyacetone is also called glycerose.
The carbon atom at which the initial
deprotonation takes place is a
stereocenter. If, for example, D-
glucose (an Aldose) rearranges to D-
fructose, the ketose, the
stereochemical configuration is lost in the
enol form. In the chemical reaction the enol can be protonated from two faces, resulting in the backformation of glucose or the formation of the
epimerD-mannose. The final product is a mix of D-glucose, D-fructose and D-mannose.
^ANGYAL, S.J.: The Lobry de Bruyn–Alberda van Ekenstein transformation and related reactions, in: Glycoscience: epimerisation, isomerisation and rearrangement reactions of carbohydrates, Vol. 215, (Ed.: STÜTZ, A.E.), Springer-Verlag, Berlin, 2001, 1–14
^de Bruyn, C. A. Lobry (1895). "Action des alcalis dilués sur les hydrates de carbone I. (Expériences provisoires)" [Action of diluted alkalis on carbohydrates I. (Provisional experiments)]. Recueil des Travaux Chimiques des Pays-Bas (in French). 14 (6): 156–165.
doi:
10.1002/recl.18950140602.
^de Bruyn, C. A. Lobry;
Van Ekenstein, W. Alberda (1895). "Action des alcalis sur les sucres, II. Transformation réciproque des uns dans les autres des sucres glucose, fructose et mannose" [Action of alkalis on sugars, II. Reciprocal transformation of the sugars glucose, fructose, and mannose into each other]. Recueil des Travaux Chimiques des Pays-Bas (in French). 14 (7): 203–216.
doi:
10.1002/recl.18950140703.
^de Bruyn, C. A. Lobry;
Van Ekenstein, W. Alberda (1896). "Action des alcalis sur les sucres, III. Transformation des sucres sous l'influence de l'hydroxyde de plomb" [Action of alkalis on sugars, III. Transformation of sugars under the influence of lead hydroxide]. Recueil des Travaux Chimiques des Pays-Bas (in French). 15 (3): 92–96.
doi:
10.1002/recl.18960150306.
^de Bruyn, C. A. Lobry;
Van Ekenstein, W. Alberda (1897). "Action des alcalis sur les sucres. V: Transformation de la galactose. Les tagatoses, et la galtose" [Action of alkalis on sugars. V: Transformation of galactose. Tagatoses and galtose]. Recueil des Travaux Chimiques des Pays-Bas et de la Belgique (in French). 16 (9): 262–273.
doi:
10.1002/recl.18970160902.
^de Bruyn, C. A. Lobry;
Van Ekenstein, W. Alberda (1897). "Action des alcalis sur les sucres. VI: La glutose et la pseudo‐fructose" [Action of alkalis on sugars. VI: Glutose and pseudo-fructose]. Recueil des Travaux Chimiques des Pays-Bas et de la Belgique (in French). 16 (9): 274–281.
doi:
10.1002/recl.18970160903.