P-D-Galactopyranosides

Methyl 2,3-di-0-acetyl-4,6-cyclo-4,6-dideoxy-p-D-galactopyranoside 2-Carb-35.2. Ring fusion methods... 

Methyl (sodium a-L-idopyranosyluronate)-(1 - 4)-(2-acetamido-2-deoxy-a-D-glucopyranosyl)-(1 ->4)-(sodium P-D-glucopyranosyluronate)-(1 ->3)-P-D-galactopyranoside... 

M. Yde and C. K. De Bruyne, Binding of substituted phenyl 1-thio-P-D-galactopyranosides to P-D-galactosidase from E. coli, Carbohydr. Res., 60 (1978) 155-165. 

Rhamnoside, a-L-rhamnopyranoside apioside, p-apiofuranoside glucoside, p-D-glucopyranoside galactoside, P-d-galactopyranoside xyloside, p-D-xylopyranoside glucuronide, p-D-glucuronopyranoside. Cinnamic acids are assumed to be in the -form. 

Licania pittieri Prance is a tree up to 15 meters high growing in the cloud forests at 1800 m in altitude. From the methanol extract of the leaves, collected in the Parque Nacional Henry Pittieri, oleanolic acid (1), ursolic acid (2), catechin (3), epicatechin (4), quercetin (5), and four glycosidic derivatives, quercetin 3-O-P-D-galactopyranoside (6), quercetin 3-O-P-D-glucopyranoside (7), quercetin 3-O-a-L-rhamnopyranoside (8), and quercetin 3-O-a-L-arabinopyranoside (9) were identified directly by comparing their spectroscopic data with those reported in the literature and/or authentic samples [see Fig. (1)] [5]. 

A solution of ethyl 1-thio- p-D-galactopyranoside (5 g, 12.9 mmol) and dibutyhin oxide (3.2 g, 13 mmol) in MeOH (500mL) was boiled under reflux for 4 h. Removal of the solvent gave a white powder that was dissolved in dry THF (500mL). r-Butyldimethylsilylchk>ride (1.95 g, 13 mmol) was added to the solution and left to stir for 24 h at room temperature, after which time TLC (9 1, CHjClj/MeOH) showed that no starting material remained. 

Method 2. A mixture of 250 mg (0.57 mmol) of 3-methoxy-2-pyridyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-p-D-galactopyranoside, 50 mg of PdfOH C, and 2 mL of EtOH was stirred under hydrogen for 5 h, at which time the starting material completely disappeared on TLC. Filtration over Celite, followed by concentration, gave the crude product, which was treated with 2 mL of pyridine and 0.12 mL of AczO at 0°C overnight. After standard workup, purification by flash chromatography on silica gel with EtOAc to EtOAc-MeOH (7 1) gave the desired product as a white solid (200 mg, 77%) mp 148°-150°C, [a]D +31.2° (c 0.33, CHClj). 

Glycosylation of 3-Methoxy-2-pyridyl 2,4-di-0-p-fluorobenzoyl-6-0-pivaloyl-(i-t>-galactopyranoside with 3-Methoxy-2-pyridyl p-D-galactopyranoside (IS)... 

To a mixture of 3-methoxy-2-pyridyl p-D-galactopyranoside (7 mg, 0.025 mmol), 430 mg (0.70 mmol) of 3-methoxy-2-pyridyl 2,4-di-O-p-fluorobenzoyl-6-O-pivaloyl-P-D-galact0-pyranoside mp 103-104°C, [a]D +57.4° (c 0.86, CHC13), and 0.25 mL of dry DMF was added 12 p,L of 1M MeOTf in CH3N02. After 20 min, 1 drop of pyridine was added, and the mixture was concentrated in vacuo. The residue was purified by flash chromatography on silica gel colnmn with EtOAc-hexane (2 1) to recover the excess of acceptor. Elution with EtOAc-MeOH (7 1) gave the desired disaccharide 26 (7.7 mg, 41%) [a]D +111.6° (c 0.4, CHClj). 

To a solution of 2-(trimethylsilyl)ethyl (methyl 5-acetamido-4,7,8,9-tetra-0-acetyl-3,4-di-deoxy-D-gfycero-a-D-gafacto-2-nonulopyranosylonate)-(2— 3)-2,4,6-tri-0-benzoyl-p-D-galactopyranoside 30 (210 mg, 0.18 mmol) and zinc chloride (30 mg, 0.220 mmol) in dichloromethane (2 mL) was added a,a-dichloromethyl methyl ether (40 jj,L, 0.434 mmol) at 0°C. The reaction mixture was stirred at room temperature for 4 h, then diluted with dichloromethane, and washed successively with cold dilute aqueous sodium carbonate solution and water, dried over NajSOj, and concentrated to give the title product (187 mg, 96%) mp 75°C, [a]D +42.36° (c 1.015, CHC13). 

D. 3-Methoxy-2-pyridyl 3,4-di-0-acetyl-2-azido-2-deoxy-p-D-galactopyranoside 458... 

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