Colette Demuynck

Enzyme-catalyzed synthesis of carbohydrates: synthetic potential of transketolase

Abstract The synthetic potential of yeast or spinach transketolases was studied, using hydroxypyruvate as a donor substrate and 31 aldehydes as acceptors. All of them react, including aromatic, heteroaromatic and α,β unsaturated aldehydes.

Enzymatic Synthesis of Natural-labeled 6-deoxy-L-sorbose Precursor of an Important Food Flavor

Abstract A biological route to natural 6-deoxy-L-sorbose is described. This method is based on the production of natural hydroxypyruvate and 4-deoxy-L-threose and their conversion into 6-deoxy-L-sorbose: hydroxypyruvate is obtained from L-serine by serine : glyoxylate aminotransferase catalysis, 4-deoxy-L-threose is obtained by microbial isomerization of 4-deoxy-L-erythrulose, this last being obtained from acetaldehyde (a naturally-available compound) and hydroxypyruvate by transketolase catalysis.

Chemoenzymatic synthesis of 6-deoxy-D-fructose and 6-deoxy-L-sorbose using transketolase

Abstract A chemoenzymatic route to 6-deoxy (D-fructose 5b and L-sorbose 5a) is described. This method is based on conversion of racemic 2,3-dihydroxybutyraldehyde to 5a and 5b catalyzed by spinach leaves Transketolase. Only the (R,R) and (R,S) isomers of 2,3-dihydroxybutyraldehyde react, yielding 6-deoxy-D-fructose and 6-deoxy-L-sorbose.

Enzymes as reagents in organic chemistry: transketolase-catalysed synthesis of d-[1,2-13C2]xylulose

Abstract Oxidation of commercial dl -[2,3-13C2]serine by d -amino acid oxidase gave [2,3-13C2]hydroxypyruvate, the condenstion of which with d -glyceraldehyde, catalysed by transketolase (partially purified from spinach leaves), gave d -threo-[1,2-13C2]pentulose ( d -[1,2-13C2]xylulose), which was studied by 13C-n.m.r. spectroscopy.

TRANSKETOLASE-MEDIATED SYNTHESIS OF 4-DEOXY-D-FRUCTOSE 6-PHOSPHATE BY EPOXIDE HYDROLASE-CATALYSED RESOLUTION OF 1,1-DIETHOXY-3,4-EPOXYBUTANE

) (2-deoxy-d,l-erythroseThe synthesis of 4-deoxyketoses in a free or phosphoryl- 4-phosphate) as the aldehydic substrate with convenientlyated form has received little attention in spite of the fact high activity, so providing access to 4-deoxy-d-fructose 6-that these compounds can serve as valuable probes for enzy- phosphate (

Chemo-enzymatic synthesis of precursors of fagomine and 1,4-dideoxy-1,4-imino-D-arabinitol

Abstract The enantioselectivity of transketolase towards, α-hydroxy-aldehydes is used to prepare compounds bearing two asymmetric centres, precursors of natural products: 2,3-dideoxynojirimycine (fagomine), 1,4-dideoxy-1,4-imino-D-arabinitol, and its oxidised form.

Rabbit muscle aldolase (RAMA) as a catalyst in a new approach for the synthesis of 3-deoxy-D-manno-2-octulosonic acid and analogues

Abstract A new approach leading to 3-deoxy-D-manno-2-octulosonic acid (KDO) and 4-deoxy-KDO is described. The key step is the formation of the C5C6 bond catalysed by fructose-1,6-bisphosphate aldolase, which controls the stereochemistry of these two centres. The important step of the aldehyde substrates (1a, 1b, 1c) synthesis is the Barbier reaction of ethyl-bromomethylacrylate or bromomethylacrylonitrile with the monoacetal of glyoxal in the presence of indium.

Fructose-1,6-bisphosphate aldolase and transketolase : Complementary tools for the de novo syntheses of monosaccharides and analogues

Abstract This paper reports a new synthesis of bromoacetol phosphate and dihydroxyacetone phosphate for use in fructose-1,6-bisphosphate aldolase (FB-aldolase) catalyzed syntheses. Then the activities of FB-aldolase and transketolase towards polyhydroxybutanal analogues of erythrose and erythrose-4-phosphate were studied. These activities were high enough to allow the syntheses of rare heptulose-1-phosphates of the d and l series.

Chemoenzymatic synthesis of chiral substituted acrylate and acrylonitrile precursors for the synthesis of 3-deoxy-2-ulosonic acids and α-methylene-γ-lactones

Abstract Substituted acrylonitrile and ethyl acrylate bearing a masked α-hydroxyaldehyde were easily synthesised by a Barbier type reaction between the monoacetal of glyoxal and bromomethyl acrylonitrile or ethyl bromomethyl acrylate. We prepared these interesting synthons in an enantiomerically pure form by enzymatic resolution with Candida rugosa lipase, or by microbial reduction of the corresponding ketones using Aspergillus niger and Lactobacillus kefir .

SYNTHESES OF L-THREOSE AND D-ERYTHROSE ANALOGUES MODIFIED AT POSITION 2

Abstract 2-O-Methyl- d -erythrose, 2-O-methyl- l -threose, 2-deoxy- d - and l -erythrose, and the corresponding acetonides have been prepared from the commercially available d -isoascorbic and l -ascorbic acids. The proportion of cyclic (α and β furanoses) and acyclic (aldehyde and hydrate) forms was determined in aqueous (D 2 O) solution by 1 H and 13 C NMR spectroscopy.