Turanose crystallization

Turanose crystallizes in well-formed prisms (see Fig. 5) it is anhydrous, shows the composition CuHhOu by combustion analysis, its melting point is 157°, and it exhibits a large and rapid mutarotation in water from an initial [a]o22 of about +22° to the final value +75.3° in the course of about thirty minutes. Isbell and Pigman26 found for the mutarotation of turanose at 20.7°, [a]n +27.3° (initial) —> +75.8°... 

Preparation 109). Melezitose is partially hydrolyzed by dilute sulfuric acid with the liberation of D-glucose and turanose. Then-glucose is removed by fermentation and the turanose crystallized directly. 

Alekhine had mentioned that turanose reacts with phenylhydrazine. Maquenne prepared the phenylosazone and described its precipitation from water in the flocculent or gel condition that is so very characteristic of the substance, but he did not report an analysis. A year after Ma-quenne s publication, Emil Fischer16 examined a small sample of amorphous turanose which had been sent by Dr. Konowaloff of Moscow. Its phenylosazone was prepared in good crystalline form by several recrystallizations from aqueous alcohol the analysis of these crystals proved conclusively the disaccharide formula for turanose which Alekhine had proposed from the analysis of amorphous substances. The writer had occasion recently to prepare turanose phenylosazone in considerable quantity its very characteristic properties and those of the derived phenylosotriazole are described on pages 27 and 28. 

The crystallization of turanose was first reported by Pacsu and the writer24 as follows In 1918 one of us (H.) found an abundant supply of the rare melezitose in a certain kind of honeydew honey and from it he prepared a small quantity of sirupy turanose in the hope of crystallizing it. Other samples of turanose sirup were prepared subsequently from this stock of melezitose by other workers in the same laboratory. Recently it was observed by D. H. Brauns that one of these sirups, the exact history of which is not now known, had crystallized after standing many years. By the use of these crystals to nucleate turanose sirups which we have lately prepared from melezitose, it has been possible to obtain a rapid crystallization of the sugar in abundant quantities. To this quotation the writer can now add the information, kindly supplied recently by Mr. C. F. Walton, Jr., that Mr. Walton prepared the other samples of turanose sirup. ... 

Turanose Phenylosazone. A mixture of 4 g. of turanose, 2 ec. of water, and 1 co. of phenylhydrazine was warmed on the steam-bath until solution was complete. To the cooled solution was added 3.5 cc. of phenylhydrazine and 4 cc. of glacial acetic acid, and the mixture returned to the steam-bath for one hour. At the expiration of this time, 40 cc. of warm 60% alcohol was added and, upon cooling, a rapid crystallization of the osazone occurred. The osazone was recovered by filtration and washed with absolute alcohol followed by ether to yield 4.2 g. (69%) of lemon-yellow needles. The osazone is soluble in hot water and separates on cooling as jelly-like particles, but water is not a satisfactory solvent for its purification. It was recrystallized from 15 parts of 95% alcohol with good recovery, as needles which melted with decomposition at 200-205° and rotated [ ]d +24.5° - +33.0° (24 hours, constant value c, 0.82) in a mixture of 4 parts of pyridine, by volume, and 6 parts of absolute ethyl alcohol. In methyl cellosolve (ethylene glycol monomethyl ether) solution it rotated C< 3d" + 44.3°— + 48.5° (24 hours, constant value c, 0.80). 

Turanose Phenylosotriazole. A solution of 15 g. of turanose phenylosazone in 300 cc. of hot water was placed on the steam-bath and a solution of 22 g. of copper siilfate pentahydrate in 150 cc. of hot water was added. The mixture turned a deep cherry-red at once and in a short time (fifteen min.) a red precipitate had formed and the solution had become green. After thirty minutes from the time of addition of the copper solution, the solution was cooled, filtered, and the copper removed as sulfide. The clear light yellow filtrate was neutralized with 45 g. of barium carbonate and the insoluble material removed by filtration. The filtrate was extracted with five 50-cc. portions of ether to remove the aniline, and the aqueous portion was concentrated in vacuo to a thick sirup. The sirup was dissolved in 60 cc. of warm alcohol, filtered to remove a slight turbidity and diluted with 65 cc. of ether. Upon cooling and scratching, the product crystallized as large prisms yield 8.9 g. (72%). The phenylosotriazole was recrystallized from 10 parts of alcohol and when pure showed the melting point 193-194° and rotated [a Jj" + 74.5° in aqueous solution (c, 0.90). 

On removal of the six acetyl groups from hexaacetylturanose methyl 1,2-orthoacetate, either by alcoholic ammonia or by a trace of sodium methoxide according to the method of Zempl n and Pacsu, crystalline turanose methyl 1,2-orthoacetate (Vlllb) was obtained. It crystallized from ethanol in the form of tabular crystals with m. p. 137 and [o]d + 114.6 in aqueous solution. Hydrolysis with alkali did not eliminate the remaining acetyl group until the methyl glycosidic group with which it was linked in the orthoester formation had been removed. The instability of the turanose methyl 1,2-orthoacetate in aqueous solution was illustrated by a gradual decrease in rotation in water from [aln +113.3 to a constant value of [a]n +72.7 in sixty-four hours. 

Fig. 5.—Crystals of turanose in polarized light. (Photographed by Mr. F. P. Phelps of the National Bureau of Standards.)...

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