Glucose dithioacetals

The glucose dithioacetal and certain others decompose at room temperature in the reaction mixture by giving alkyl 1-thioglycopyranosides. This class of compounds has gained a certain importance in the synthesis of oligosaccharides (reaction 10.4). They are prepared more commonly in the peracetylated form as 6J, by treating the )3-peracetate of the pyranose with a thiol in the presence of BF3.OEt2. 

In the literature are several reports of acid-catalyzed reactions of dithioacetals, or of reactions leading to dithioacetals, where episulfonium ions may be involved. The reaction of the substituted n-glucose dithioacetal... 

Intramolecular cyclization of the Ai-benzyloxycarbonylamino-o-glucose dithioacetal 542 with sodium methoxide gave the 5-(alditol-l-yl)oxazolidin-2-one 543 with elimination of a molecule of benzyl alcohol (67CB2655) (Scheme 143). 

Phenyl glucoside iV-Arylglucosamine V-Carboethoxyglucosamine Glucose dithioacetal Gulose Derivatives Gulose... 

Thus the D-glucose dithioacetal 6 gave pentodialdose 7 (Scheme 1). Ethereal periodic acid has been used to selectively cleave terminal 0-isopropylidene groups and hence to cleave the released diols in a one pot process. Thus di-O-isopropylidene mannose derivative 8 gave the pentodialdose ester 9. Periodic acid has also been used to leave methyl a-D-xylopyranoside only at the C-2 - C-3 site. ... 

D-Glucose propane-1,3-diyl dithioacetal (1 S)-D-Glucose S-ethyl... 

Like D-glucose and D-fructose, however, D-xylose can be utilized chemic ly or microbially—to generate a variety of interesting five-ca n c emica s o er than furfural (vide supra) or xylitol, a noncaloric sweetener, both being duectly produced from xylan hydrolysates, that is, without the actual isolation of the sugar. Other readily accessible intermediate products of high preparative utiUty (Scheme 2.14) are the open-chain fixed dithioacetal, the D-xylal, and D-hydroxy-xylal esters, or pyrazol or imidazol A -heterocycles with a hydrophilic trihydroxypropyl side chain. 

In attempting to obtain 2,5-anhydro-D-glucose diethyl dithioacetal, Defaye58 performed the nitrous acid deamination of 2-amino-2-deoxy-D-glucose diethyl dithioacetal (27) under weakly acidic conditions (acetic acid and sodium nitrite), and obtained a principal product later shown59 to be ethyl 2-S-ethyl-l,2-dithio-a-D-mannofuranoside (28). Shortly before, Horton and coworkers60 had reported the forma-... 

Solvent can have a marked effect on deamination in other respects. For example, it is commonly found that the extent of rearrangement is greater, the more polar the solvent 29,44 45 this effect is attributed to the increased lifetime of carbonium-ion species and their rearrangement to species that are more thermodynamically stable. Reactions performed at different pH values may also give different products, as illustrated by the deamination of 2-amino-2-deoxy-D-glucose diethyl dithioacetal hydrochloride in solution in (a) aqueous acetic acid and (b) hydrochloric acid (see p. 65). 

In related work,2123 2-amino-2-deoxy-D-glucose ethylene dithioacetal was deaminated at different pH values. In a system buffered at pH 5, three main products were isolated after the mixture... 

A solution of the dry D-glucose diethyl dithioacetal (10.725 g 37.5 mmol) 2-methoxypropene (3.245 g 45 mmol) in anhydrous DMF (130 mL) and p-toluenesulfomc acid (375 mg) was kept for 68 h at 0°C. The homogeneous mixture was kept with exclusion moisture until TLC indicated that all the starting material had reacted, and it was then poured into a solution of sodium hydrogenocarbonate (2% w/v, 60 mL). This mixture was extracted with ether (4 x 30 mL). The combined ether extracts woe washed with water (2 x 30 mL), dried (magnesium sulfate), and evaporated, giving yellowish crystals (8.275 g, 68%) that were recrystallized twice from dichlorometbane petroleum ether to give colorless crystals of 14 yield 5.735 g (47%), mp 73J-74.5°C, [a]D-ll° (c 2.027, methanol). 

M. 2-Anrino-2-deoxy-i>-glucose propan-l,3-diyl dithioacetal ... 

P. Ang eaad, C Bosso, 1. Defaye, a Horton, C Gohen-Addad, and M. Thomas, Vichtal participation in the nitrous add deamination of chiral 1 -thk>-2-amtnoalkanepolyols dm deamination of 2-amino-2-deoxy-D-glucose ethylene and propan-1,3-diyl dithioacetals, J. Chan. Soc. Pertiiu Trans. 1 1383 (1979). 

The V and A A series in the mass spectra of 2-deoxy-D- glucose" diethyl dithioacetal and L-rhamnose diethyl dithioacetal are shifted 14 mass units,... 

Although dithioacetals of D-glucose do not form the n-glucofuranosides, those of 2-deoxy-D-arabino-hexose do Stacey and coworkers80 were able to convert the dibenzyl dithioacetal into a mixture of the methyl 2-deoxy-D-araWno-hexofuranosides. Thus, the C-2 hydroxyl group has a bearing on the course of the reaction. 

The formation of these products from the dialkyl dithioacetals falls into two categories. The first group comprises compounds readily formed (or isolated), and is confined to derivatives of D-glucose, D-glucuronic acid, 2-acetamido-2-deoxy-D-glucose, and D-ribose. The products are obtained in high yield the formation is generally accomplished in aqueous solution, with one mole of mercuric chloride per mole of dithioacetal, and the solution is kept neutral. 

Dithioacetals have also been used as precursors for the transacetalization. Thus, both diastereomers 213 and 214 have been prepared from glucose-derived dithioacetal 212 and rac-230 and used for the efficient resolution of rac-Y)l (Scheme 60) <1995TA295>. 

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