P-D-Galactoside

Fig. 72. AB2-based polyazides used in click chemistry with propargylated p-D-galactosides and a-L-fucosides.427...

Not only chiral separations have been achieved with Mi-stationary phases. It has also been demonstrated that the MIP could distinguish between ortho- and para-isomers of carbohydrate derivatives. For example, a polymer imprinted with o-aminophenyl tetraacetyl P-D-galactoside was used to analyze a mixture of p-and o-aminophenyl tetraacetyl P-D-galactoside. As expected, the imprinted ortho analyte eluted after the non-imprinted para component see Fig. 5. Although baseline separation was not obtained, a separation factor of a = 1.51 was observed [19]. 

Although we show only the methyl p-D-galactoside as a product, some of the a epimer will also be formed because the carbocation intermediate can be attacked at either face by the methanol. 

Regioselective acylations can also be achieved by the stannylene procedure but, in general, selectivities are not as high as for alkylations. For example, treatment of methyl P-D-galactoside with dibutyltin oxide followed by reaction with benzoyl chloride results in the formation of a mixture of methyl 6-O-benzoyl-P-D-galactoside (53%) and methyl 3,6-O-di-benzoyl- P-D-galactoside (21 %).40... 

This enzyme catalyzes the hydrolysis of P D-galactosides and a-L-arabinosides. It is best known for its action in hydrolyzing lactose and is, therefore, also known as lactase. The enzyme is widely distributed and occurs in higher animals, bacteria, yeasts, and... 

The statement does apply sometimes, however, in the borderland between reactions in vivo and in vitro thus in studies of enzyme action, W. W. Pigman (J. Am. Chem. Soc., 62, 1371 (1940) J. Research Natl. Bur. Standards, 26, 197 (1941)) has found that phenyl D-manno- -n-gaZa-heptoside is slowly hydrolyzed by the emulsin of sweet almonds, which also hydrolyzes phenyl P-D-galactoside. For literature references on the subject see an article by Mildred Adams, N. K. Richtmyer and C. 8. Hudson, J. Am. Chem. Soc., 65, 1369 (1943). 

The enzyme and inhibitor were incubated for 10 minutes at 20°, and the reaction was started with o-nitrophenyl p-D-galactoside (10 A/) citrate-phosphate buffer pH 5.3. 

Demchenko, A V, Kamat, M N, De Meo, C, S-Benzoxazolyl (SBox) glycosides in ohgosaccharide synthesis novel glycosylation approach to the synthesis of p-D-glucosides, p-D-galactosides, and a-D-mannosides, Synlett, 1287-1290, 2003. 

Substrate solution Dissolve 4-methylumbelliferyl P-D galactoside (0.2 mg/mL) in PBS by gentle warming. Filter through filter paper and then add 1 M MgCl2 solution to give a final concentration of 10 mM. 

Gal actosidase (E.C.3.2.1.23) catalyzes the hydrolysis of terminal nonreducing (5-D-galactose residues in (5-o-galactosides. This enzyme has a molecular weight of 540 kDa, a pH optimum of 7.0 and a specific activity (37 °C) of600 U/mg. A synthetic substrate, o-nitrophenyl-p-D-galactoside, yields readily detectable o-nitrophenol upon hydrolysis (Eq. 6.12) ... 

Galactosidase. (EC 3.2.1.23) is an enzyme found in many bacterial and eukaryotic cell types that converts o-nitrophenyl P-D-galactoside to o-nitrophenol and D-galactose. It will also convert 5-bromo-4-chloro-3-indoyl... 

The activity of -galactosidase is usually measured with the fluorogenic substrate 4-methylumbelliferyl-p-D-galactoside, for example, 1 mAf in 50 mM citrate/0.1 M phosphate buffer, pH 4.0, with O.IM NaCl (Suzuki, K 1977). (The high ionic strength is needed to stabilize the enzyme.) One unit of 3-galactosidase is generally defined as the amount of enzyme that splits 1 fcmol of this substrate per minute under the above conditions, at 37°C. 

Various tripeptides (112) containing serine p-D-galactosides have been examined for base stability. Replacing H by Me at had no effect, but a similar change at R caused appreciable increase in the rate of p-elimination, suggesting that the carbonyl group labelled A acts as a base to remove the illustrated proton and induce p-elimination of the sugar. ... 

---