Butyl D-glucopyranosides

From the systematic study of the glycosylation reaction, a kinetic scheme involving both consecutive and competitive steps has been proposed (Figure 7.1). Butyl-D-glucofuranosides and butyl-D-glucopyranosides are primary products, butyl-D-glucofuranosides being then quantitatively converted into their pyranoside form. 

Another important feature between H-Y and H-Beta zeolites is the difference observed for the (Ha. ratio of butyl-D-glucopyranosides versus D-glucose conversion (Figure 7.2). The fi/a ratio of pyranosides is higher for H-Y (Si/Al = 15) than for H-Beta (Si/Al =12.5) up to a glucose conversion of 80%. At complete glucose conversion, the thermodynamic (Ha ratio of 0.5 is obtained. 

Figure 7.2 Plot of the [i/a ratio of butyl-D-glucopyranosides versus D-glucose conversion in the presence of different catalysts [ , H-Y (Si/Al = 15) A, H-Beta (Si/Al = 12.5)] for glycosylation of glucose (4.8 g) with n-butanol (50 ml) at 383 K and 1000 rpm agitation speed. Reprinted from J. Catal., Vol. 185, Chapat et al., pp. 445-453, Copyright 1999, with permission from Elsevier...

Figure 1. Time conversion plot of D-glucose (1, O) to butyl-D-glucofuranosides (12, A) and to butyl D-glucopyranosides (13, ) at 383 K in the presence of Beta zeolite.

The same authors [56] performed a systematic study of the acetalization of glucose with 1-butanol in the presence of HY zeolite and proposed a kinetic scheme for the glycosylation reaction involving both consecutive and competitive steps. Butyl D-glucofuranosides (12) and butyl D-glucopyranosides (13) are primary products and butyl D-glucofuranosides are then converted quantitatively into their pyranoside form (Scheme 6). 

J.-F. Chapat, A. Finiels, J. Joffre, and C. Moreau, Synthesis of butyl-a and / -d-glucopyranosides in the presence of dealuminated H-Y faujasites Kinetic study, mechanism, stereoelectronic effects, and microreversibility principle, /. Catal., 185 (1999) 445—453. 

Koch and coworkers49 found that the C-l shifts of isopropyl and tert-butyl a-D-glucopyranoside respectively lie 4 and 7.7 p.p.m. to higher field than that of the methyl glycoside this was assumed to be wholly due to the y-effect between methyl groups of the aglycons and the an-omeric centers. Isopropyl a-D-glucopyranoside can exist as three retainers 3, 4, and 5, and it may be seen that the last two contribute to... 

Fabre, J. Betbeder, D. Paul, F. Monsan, P. Perie, J. Versatile enzymatic diacid ester synthesis of butyl a-D-glucopyranoside. Tetrahedron 1993, 49, 10877-10882. 

All these substances reduce hot Fehling solution, though the anilide LXXIX required heating at 95° for two minutes. Treatment with 0.003 M barium methoxide in dry methanol at room temperature decomposed 3-keto-n-butyl 0-D-glucopyranoside tetraacetate (X), to yield D-glucose and methyl vinyl ketone (LXXX). 

The mechanism of beta-activation described above has been substantiated by the observations that 4-hydroxypentanal /S-D-glucopyranoside (3-formyl-l-methylpropyl /3-D-glucopyranoside) (LXXXI)61 as well as the 18-D-glucopyranosides of the propyl (LXXXII) and butyl (LXXXIII) analogs of XI62 are stable in alkaline solution. 

RX. n-butyl bromide n-dodecanyl iodide cyclohexyl iodide ethyl bromo acetate methyl 2,3-di-O-acetyl-4-O-benzoyl-6-bromo-6-deoxy-ot-D-glucopyranoside methyl 2,3,4-tri-0-acetyl-6-deoxy-6-iodo-0 -D glucopyranoside l,2 3,4-di-0-isopropylidene-6-deoxy-6-iodo-a-D-galactopyranose methyl 2(R)-[(tert-butoxycarbonyl)amino]-3-iodo-propionate cyclic bis(trifluoromethyl)oxazolidinone bromide. 

In our research group the glycosylation reaction between D-glucose and n-butanol was investigated over a dealuminated H-Y zeolite with a Si/Al ratio of 15.[45, 46] In this way, butyl-D-glucofuranosides and glucopyranosides are readily synthesized, at temperatures from 90 to 110 °C, with 6 wt% of catalyst and with a butanol/glucose ratio from 5 to 40. 

In the crystal, trimethyltin methoxide is a linear polymer, and dimethyltin dimethoxide is a dimer. The cyclic dialkyl-l,3,2-dioxastannolanes, which are formed from 1,2-diols, are important in regiospecific synthesis, particularly in carbohydrate chemistry. Their degree of association is determined by steric factors in the solid state, l,l-di-n-butyl-l,3,2-dioxastannolane is a 6-coordinate ribbon polymer, but the di-tert-butyl analog is a 5-coordinate dimer (19). Methyl 4,6-0-benzylidene-2,3-C-dibutylstannylene-Q -D-glucopyranoside is a 5-cordinate dimer, but methyl 4,6-0-benzylidene-2,3-0-dibutylstannylene-Q -D-mannopyranoside is a pentamer containing three, medial, 6-coordinate and two, terminal, 5-coordinate tin atoms. 

The rate constant for the hydrolysis of tert-butyl /S-D-glucopyranoside is about 1000 times as great as that for methyl -D-glucopyranoside in 1 M perchloric acid at 25°. TimelF found the factor to be about 500 in... 

An early application is the preparation of 6-O-acylglucopyranosides (sugar esters) (Scheme 13.1). CALB was found to chemoselectively esterify the primary 6-OH with fatty acids. Ethyl D-glucopyranoside was initially selected due to improved solubility in neat fatty acid [44], but reactions with unmodified mono- and disaccharides suspended in acetone, tert-butyl alcohol or DMSO-mixtures have also been reported [45], The products have found applications as non-ionic tensides. 

It seems reasonable to assume that this is the normal route for acidic hydrolysis of pyranosides. Exceptions include the hydrolyis of tert-butyl (3-D-glucopyranoside, which is cleaved at the oxygen-ferf-butyl bond.215... 

C. Armour, C. A. Bunton, S. Patai, L. H. Selman, and C. A. Vernon, Mechanism of reaction in the sugar series. III. Acid-catalyzed hydrolysis of tert-butyl fi-D-glucopyranoside and other glycosides, J. Chem. Soc., (1961) 412-416. 

These authors also found that the use of microporous catalysts significantly increases stereoselectivity for butyl jff-D-glucopyranosides [50,56], For instance, the pi a ratio of pyranosides is ca 1.5 for zeolite HY (Si/Al = 15) and ca 0.7 for Beta (Si/Al 12.5), whereas for p-toluenesulfonic acid the p a ratio is intermediate, ca 1. At nearly complete conversion of glucose, however, a thermodynamic ratio p a of 0.5 is obtained. The kinetic reaction scheme proposed by the authors, involving... 

The regioselective primary malonylation of phenyl P-D-glucopyranoside, serving as model substrate for natural glycoconjugates, has been accomplished by treatment with malonic acid in an aprotic solvent in the presence of tert-butyl... 

Armour C, Bunton CA, Patai S, Sehnan LH, Vernon CA (1961) Mechanisms of reactions in the sugar series. Part III. The acid-catalysed hydrolysis of t-butyl p-D- glucopyranoside and other glycosides. J Chem Soc 412-416... 

Methyl 2,3, -tri-O -butyl-a-D-glucopyranoside has been synthesized by selective protection at -6 (>85%) with dihydropyran (H -DMSO) followed by phase-transfer catalyzed alkylation and hydrolysis. The 2,3,, 6-tetra-O -butyl ether was also synthesized. ... 

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