β-1-N-acetamido-D-glucopyranose (2), a model of N-glycoprotein linkage region, and its benzamido analogue were explored as novel acceptors in transglycosylation catalysed by β-galactosidase from Bacillus circulans. Acceptor ability of 2 was shown to be as good as or better than several O- glycosides employed earlier. Systematic variation of reaction conditions led to improvement of yield from 5 % to 41 %. Interestingly, use of aqueous organic media has led to increased yield of transglycosylation and the 1,3- linked disaccharide was formed in considerable amounts under all the conditions examined.

Kuttikode Priya

Duraikkannu Loganathan

aminosugar

BETA 1 N ACETAMIDO DEXTRO GLUCOPYRANOSE

beta galactosidase

disaccharide

glycoprotein

glycosidase

glycoside

GLYCOSYLASPARAGINE

oligosaccharide

organic compound

unclassified drug

aqueous solution

article

BACILLUS CIRCULANS

catalysis

glycosylation

nonhuman

priority journal

reaction analysis

stereochemistry

structure analysis

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

β-Galactosidase catalysed transglycosylation in aqueous organic media using glycosylasparagine mimics as novel acceptors

Tetrahedron

Glycosidases are valuable catalysts for the synthesis of a wide array of di- and oligosaccharides. Herein we report on the use of β-1-N-acetamido-2- acetamido-2-deoxy-d-glucopyranose, the simple model of the N-glycoprotein linkage region, as a novel acceptor for disaccharide synthesis catalyzed by β-N-acetylhexosaminidases from Aspergillus oryzae and mung beans (Vigna radiata) under transglycosylation as well as reversed hydrolysis. The exclusive formation of the disaccharide model, β-d-GlcNAc-(1→4)-d- GlcNAcβNHAc, by transglycosylation and the corresponding (1→6) analog under reversed hydrolysis both in reasonable yields demonstrates the versatility of β-N-acetylhexosaminidase from Aspergillus oryzae. The efficacy of the enzyme from Vigna radiata for synthesis has been demonstrated for the first time. This is also the first report on the use of derivatized sugars as co-reactants in glycosidase catalyzed reversed hydrolysis mode of synthesis. The excellent (1→6) selectivity of mung beans β-N-acetylhexosaminidase under transglycosylation and that from Aspergillus oryzae under reversed hydrolysis would prove to be very useful. © 2004 Elsevier Ltd. All rights reserved.

Tetrahedron Asymmetry

Enzymatic synthesis of N-glycoprotein linkage region disaccharide mimetics using β-N-acetylhexosaminidases from Aspergillus oryzae and Vigna radiata

The stability of almond β-glucosidase in five different organic media was evaluated. After 1 hour of incubation at 30°C, the enzyme retained 95, 91, 81, 74 and 56% relative activity in aqueous solutions [30% (v/v)] of dioxane, DMSO, DMF, acetone and acetonitrile, respectively. Transglucosylation involving p-nitrophenyl β-D-glucopyranoside as donor and β-1-N-acetamido-D-glucopyranose, which is a glycosylasparagine mimic, as acceptor was explored under different reaction conditions using almond β-glucosidase and cloned Pichia etchellsii β-glucosidase II. The yield of disaccharides obtained in both reactions turned out to be 3%. Both enzymes catalyzed the formation of (1 → 3)- as well as (1 → 6)-regioisomeric disaccharides, the former being the major product in cloned β-glucosidase II reaction while the latter predominated in the almond enzyme catalyzed reaction. Use of β-1-N-acetamido-D-mannopyranose and β-1-N-acetamido-2-acetamido-2-deoxy-D-glucopyranose as acceptors in almond β-glucosidase catalyzed reactions, however, did not afford any disaccharide products revealing the high acceptor specificity of this enzyme. © 2004 Taylor & Francis Ltd.

Biocatalysis and Biotransformation

Transglycosylation catalyzed by almond β-glucosidase and cloned Pichia etchellsii β-glucosidase II using glycosylasparagine mimetics as novel acceptors

Crystal structures of 1-N-(β-D-glucopyranosyl)chloroacetamide (1), an inhibitor of glycogen phosphorylase, and the corresponding galactopyranosyl amide (2) have been determined. Both crystals belong to P212 121 space group with 1 having the unit cell dimensions of a = 7.939(3), b = 9.547(3) and c = 14.157(2) Å, while those of 2 are, a = 7.636(10), b = 9.004(8) and c = 14.807(5) Å. The sugar ring takes a 4C1 conformation and the amide linkage exists in Z-anti conformation in both crystals. The torsion angle O5-C1-N1-C1′ is -93.9(5) for 1 and -111.5(3)° for 2. The conformational preference of Cl and N1 in 1 and 2 is found to be between anti and gauche. The molecular assembly in both 1 and 2 is stabilized by a finite chain of hydrogen bonds starting from N1H and ending at O1′, whereas a ten membered hydrogen-bonded ring involving O4H and O5 is observed in 1.

Journal of Carbohydrate Chemistry

Crystal Structures of β-1-N-Chloroacetamido Derivatives of D-Glucose and D-Galactose

Equilibrium tautomeric mixtures of several mono- and disaccharides are obtained in anhydrous form, without the use of water, by reacting the commercially available reducing sugars with ammonia gas in dry methanol, followed by the concentration of the resultant solution to dryness. Mutarotation and hydrolysis of the initially formed glycosylamine in the resultant medium account for the transformation. Equilibrium anomeric mixtures enriched in the β-form of commercially available sugars such as α-D-glucose and α-lactose have not only vastly increased solubility, but are also synthetically valuable as these can be readily converted to the methyl/benzyl/trimethylsilyl ether and other derivatives for further transformations. © 2002 Elsevier Science Ltd. All rights reserved.

Carbohydrate Research

A method for obtaining equilibrium tautomeric mixtures of reducing sugars via glycosylamines using nonaqueous media

Journal	Tetrahedron
ISSN	00404020
Open Access	No