Glucosyl bromide

The first examples of C-disaccharides obtained applying radical C-glyco-sylation of sugar-derived exocyclic enones was reported by Giese and Witzel.138 The reaction of glucosyl bromide 148 and enone 154 afforded a mixture of stereoisomeric C- glucopyranosyl compounds from which pure 155 was obtained in 22% yield by precipitation (Scheme 52). 

Gentiotetraose, an all ()-(I —>6)-l inked tetramer of glucose was selectively prepared by Gagnaire and coworkers (Scheme 1.4).19 6-0-Trichloroacetylated glucosyl bromide 27 was attached to succinoylated 2% crosslinked polystyrene. After selective... 

We therefore needed a ready synthesis of the 1,6-epithio epoxide 119. Normally, for such syntheses, the sulftir atom is introduced at an early stage [64]. However, it appeared to us that a suitable doubly-activated sugar such as 120 should be capable of direct conversion to the 1,6-epithio sugar 121 by treatment with some type of sulfur reagent. Indeed, the o-glucosyl bromide 122 was easily prepared and, upon treatment with either hydrogen sulfide and triethylamine in DMF or benzyltriethylammonium tetrathiomolybdate in chloroform, gave the... 

It is noteworthy that all attempts to convert 275 into the corresponding D-glucosyl bromide with hydrogen bromide in acetic acid were unsuccessful, because the reagent was also attached to the 2-(thiocyanato) group. Treatment of 275 with titanium tetrachloride in chloroform afforded crystalline 3,4,6-tri-0-acetyl-2-deoxy-2-(thiocyanato)-a-D-glucosyl chloride (277)... 

If, in the foregoing reaction of glycosyl bromides, the methanol is replaced by moist acetone, exchange of the bromide ion for hydroxyl takes place. For example, 2,4,6-tri-0-acetyl-3-0-tosyl- -D-glucosyl bromide gives19,242 2,4,6-tri-0-acetyl-3-0-tosyl-j8-D-glucose ... 

Despite the fact that 2,4,6-tri-0-acetyl-3-0-tosyl-a-D-glucosyl bromide reacts86 with silver p-toluenesulfonate in pyridine to give a glucosyl-pyridinium p-toluenesulfonate (see, also, p. 120), it is claimed237 that treatment of 3,4-di-0-acetyl-2,6-di-0-tosyl-a-D-glucosyl bromide with silver acetate in pyridine (at 50° for only 2 minutes) affords 1,3,4-tri-O-acetyl-2,6-di-0-tosyl-/3-D-glucose. 

Composition of Products from Reaction of Tetra-O-acetyl-a-o-glucosyl Bromide with Methanol in the Presence of Silver Carbonate10... 

An amount of 40 g. of 2,3,4,6-tetra-O-acetyl-a-D-glucosyl bromide is warmed with 12 g. of diethylamine in 20 ml. of dry benzene at 60° until dissolved. (Benzene is often replaced by chloroform, and the initial warming is often omitted.) After 32 hours at room temperature, the reaction mixture is extracted with dry ether, and the diethylamine hydrobromide is removed by filtration. The filtrate is washed once with dilute sulfuric acid and twice with water and is dried over calcium chloride. After evaporation of the ether under diminished pressure, the residue is dissolved in the least possible amount of hot alcohol. Crystallization occurs after the addition, with stirring, of petroleum ether to the cooled solution. Yield of crude 2,3,4,6-tetra-0-acetyl-(2-hy-droxy-D-glucal), 17 g. (51% of the theoretical). Itecrystallization is effected from hot water or from ethanol with the addition of water to turbidity.1 2... 

Tetra-O-acetyl-D-glucosyl bromide (4.1 g.) and sarcosine ethyl ester (2.4 g.) were warmed together on a waterbath at 50° and the mixture became dark-brown. The sirup was kept at room temperature for 20 hours, whereupon crystals formed. Dry ether was added, sarcosine ester hydrochloride was removed by filtration, and the solution was quickly washed with water and dried. Removal of the ether gave a yellow sirup which, on treatment with methanol, gave needles of tetra-O-acetyl-iV-D-gluco-sylsarcosine (3.5 g., 79% yield) after recrystallization from methanol, m.p. 87-88° (no dec.). This compound was treated at 0° with methanol (100 ml.) saturated with ammonia. After removal of the solvent, crystals of A-D-glucosylsarcosine (1.7 g., 88% yield), m.p. 169-170°, were obtained. 

Chemical synthesis of 1-phosphate esters of 2-amino-2-deoxy-n-glucose has been described.37 127 Reaction of 3,4,6-tri-0-acetyl-2-amino-2-deoxy-a-D-glucosyl bromide hydrobromide (XLII) with triethylammonium diphenyl phosphate gave the l-(diphenyl phosphate) ester, isolated as its hydrochloride (XLIII). Cleavage of the phenyl groups and subsequent deacetylation gave 2-amino-2-deoxy-D-glucosyl phosphate as the crystalline, dipolar-ionic, monopotassium salt (XLV). 

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