Methyl P-£>-glucopyranoside

Figure 4.27 500 MHz NOE spectra of methyl p-glucopyranoside in DMSO-de (a) irradiation of the anomeric hydrogen (fi 4.42), giving enhancement of the methoxy signal and ring hydrogens (red) (b) irradiation of the methoxy signal (fi 3.60), giving enhancement of the anomeric position (red)...

Microbial metabolism studies on sampangine have resulted in the isolation and characterization of two metabolites, sampangine-4 -0-methyl-P-glucopyranoside (SAMMl) and sampangine-P-glucopyranoside (SAMM2). 

Separation selectivity can also be altered by the type of ion that is formed for the compound of interest. Cation or anion adducts can have a significant effect on the separation. In the positive ion mode, most ions formed from electrospray or any chemical ionization methods are protonated cations. However, if Na+ is added to the electrospray solution, sodiated adducts may be formed as the primary response ion. For example, the protonated ions of two isomers, methyl-P-glucopyranoside and methyl-a-glucopyranoside, cannot be baseline separated in DTIMS, but the sodiated adducts of the same isomers can be baseline separated. Figure 8.9 demonstrates separation selectivity induced by cation adduction. These IMS spectra are of the methyl-p-D-galactopyranoside and the methyl-a-D-galactopyranoside isomers adducted with cobalt acetate, silver, and lead acetate. The cobalt acetate adducts had a separation factor of 1.02, the silver adducts had a separation factor of 1.05, and the lead acetate adducts had a separation factor of 1.07. 

An extract from Lactuca indica showed significant free radical scavenging activity, and protected phixl74 supercoiled DNA against strand cleavage and reduced oxidative stress in human promyelocytic leukemia HL-60 cells. On account of protocatechulic acid, methyl p-hydroxybenzoate, caffeic acid, 3,5-dicaffeoylquinic acid, luteolin 7-O-fT glucopyranoside, and quercetin 3-0-(3-g 1 ucopyranoside are the major antioxidative constituents (111). 

The 3-0-benzyl derivative underwent a rapid reaction with TASF at reflux temperature to give methyl 3-0-benzyl-A,6-0-benzylidene-2-deoxy-2-fluoro-p- -glucopyranoside (J ) in A5% yield, and a minor product (19% yield) tentatively assigned the structure of methyl 3-0-benzvl-A.6-0-benzvlldene-2-deoxv-B-D-ervthro-hex-2-enopyranoslde. Base-catalyzed elimination reactions with trlflyl derivatives are uncommon (, ), but have been observed In certain furanoid (A0,A2) and, recently, in pyranoid (33,35) ring systems (see also Table I). Eliminations in glycopyranosldes occurred (33,35) under conditions which decreased the ease of nucleophilic substitution (33,A3,AA). 

T. Nishimura and M. Ishihara, Action of fungal p-glucosidase on the mono-O-methylated p-nitrophe-ny 1 p-D-glucopyranoside, Holzforschung, 63 (2009) 47-51. 

Methyl-p-D-glucopyranoside Methyl-a-D-glucopyranoside Minor product Major product... 

Methyl-p-D-glucopyranoside (9.7 g) was benzylidenated as described in the foregoing. After removal of the solvents, the cake of product was broken up with a spatula, and dissolved in a solution of sodium hydrogen carbonate (1 g) in water (150 mL) and ethanol (150 mL) by heating on a boiling-water bath. The solution was cooled to 4°C, and compound 20 was filtered off, washed well with water, and dried for 30 h at 30°. The product (8.2 g, 58%) had an m.p. of 207-208.5°C (unchanged by recrystallization from ethyl alcohol) and [ajp —76° (c 1.0, methanol). 

D. Reaction of Methyl p-D-Glucopyranoside with Sulfuryl Chloride [47]... 

In a 100-ml conical flask place 5.5 g (0.015 mol) of methyl 2,3,4,6-tetra-O-acetyl-/ -D-glucopyranoside (Expt 5.111), 50 ml of dry methanol and 10ml of a solution of sodium methoxide in methanol previously prepared by the cautious addition of 0.1 g of sodium to 20 ml of methanol. Stopper the flask and allow the solution to stand for 1 hour, then add sufficient ion exchange resin [Zeolite 225 (H )] to render the solution neutral to moist universal indicator paper. Remove the resin by filtration, wash with methanol and evaporate the combined filtrate and washings under reduced pressure (rotary evaporator). Triturate the colourless syrup with absolute ethanol to cause it to solidify and recrystallise from absolute ethanol. The pure methyl / -d-glucopyranoside has m.p. 108-109 °C, [oc]d° —30.2° (c2.8 in H20) the yield is 2.4 g (83%). 

OH-2 and OH-3 in methyl 4-O-methyl-p-D-xyIopyranoside [28] or alkyl 4,6-0-benzylidene-(3-D-glucopyranoside [29] (cf. Ref. [30] for discussion of the discrepancy observed, see Ref. [10]). This preponderance of position 2 over 3 appears also in methyl 4,6-O-benzylidene-a-D-mannopyranoside, the axially oriented hydroxyl group being substantially more reactive than the equatorial one [31-33]. Some 55% of 2-0-benzyl and 19% of 3-Obenzyl derivative have been isolated, together with 10% of 2,3-di-O-benzyl and 16% of the starting material [33]. 

From methyl a-D-glucopyranoside, 55% of 2-O-benzyl and 18% of 3-O-benzyl derivatives could be obtained using 1,4-dioxane as a solvent. No monobenzyl derivative was observed under standard DMF solvent conditions [131]. Conformational equilibria 4Ct XC4 play a role in the results of alkylation of all-equatorial methyl P-D-xylopyranoside and methyl P-D-glucopyranoside [131]. 

Selective tritylation of methyl oc-L-rhamnopyranoside yielded 57% of the 3-0-trityl derivative, together with 1 % of the 2-0- and 3 % of 4-0-trityl isomers. For methyl P-L-rhamnopyranoside, 34% of the 3-trityl and 17% of the 4-trityl ether were obtained [315]. Similarly, the 3,6-ditrityl ether is the major product of ditrityl-ation of methyl and benzyl a-D-mannopyranosides [316]. The corresponding a-D-glucopyranosides yielded the 2,6-di-O-trityl derivative, whereas both the 2,6- and 3,6-ditrityl ethers were isolated in the case of [Pg.237]

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