Pyranosides substrates

More striking is the binding of the lactone III to /TV-acetyl-D-glucosaminidase. The dissociation constant of 5 X 10 7 M is 4000 times smaller than the KM of 2 X 10-3 M for the pyranoside substrate V.12 However, it is possible in this example that the enzyme forms a covalent bond with the analogue so that the tight binding does not result solely from noncovalent binding.13... 

Scheme 20 Borinic acid-catalyzed monoacylations, sulfonylations and alkylations of cw-l,2-diol groups in pyranoside substrates...

Unsubstituted glycal 49 underwent cycloaddition reaction with a sp dienophile (maleic anhydride) in refluxing toluene to give a mixture of two epimeric compounds arising from an expected endo attack. The 7 3 ratio in stereoadducts 51 and 52 clearly indicates an stereochemical preference inherent to the pyranosidic substrate (vide supra). 

Tissue source Age, years p-Nitrophenyl- D-galacto- pyranoside Substrate nmoles hydrolyzed per mg of protein per hr ... 

IC with bovine enzyme which is very similar to the human one. Inhibitor concentration for 50% inhibition. K of substrate (phenyl a-D-mannopyranoside). K of substrate (4-nitrophenyl a-D-manno-pyranoside). K of substrate (4-nitrophenyl D-glucosiduronic acid). K of substrate (4-nitrophenyl 2-acetamido-2-deoxy- o-glueoside). Inhibitors were chitotetraono-1,5-lactone and chitotetraose, respectively. 

For definition of k3 see equation 2 substrates used o-cresyl /3-D-gluco-pyranoside and o-cresyl /3-n-galactopyranoside. 

Substrate/buffer solution dissolve 1.70 mg 4-methylumbelliferyl-jS-D-galacto-pyranoside (MW 338.3) in 10 ml of reaction buffer to a final concentration of... 

Quantum yields were determined, and the mechanism was discussed as a function of the temperature of the reaction, the structure of the substrate, and the effect of the dissolved oxygen. The formation of the 4- and 6-O-benzoyl derivatives 65 and 66 was later confirmed,87 and preliminary experiments conducted on methyl 2,3 4,6-di-0-ben-zylidene-a-D-mannopyranoside and on methyl 2,3-di-O-benzoyl-4,6-O-benzylidene-a-D-gluco- and -galacto-pyranosides were reported.88 Further results in the field were obtained for an O-ethylidene deriva-... 

The stereoselectivity in cyclizations of vinyl ether systems to form furanosyl disaccharides is controlled by both the side chain substituent (1,4-asymmetric induction) and the configuration of the existing pyranoside linkage (equation 49).142 Substrates with no side chain substituent show no stereoselectivity. 

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