Melezitose turanose

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 is readily purified by recrystallization from hot methyl alcohol, in which it is moderately, though slowly, soluble. In preparing the sugar, the first stage of the hydrolysis of melezitose by an acid solution is carried out under well controlled conditions, and is followed by the removal of the D-glucose from its mixture with turanose. This is usually accomplished by a selective fermentation with yeast, but an... 

The establishment of the structure of turanose furnishes a firm basis for an eventual determination of the structure of melezitose. One can start with the assurance that the trisaccharide is 8-[a-v-glucopyranosyVy D-fructose < > n-glucopyranose this formula requires three further specifications. The first of these is an allocation of a ring to the fructose unit, the second is a decision between the a- and /S-forms for this unit, and the third is a similar decision between these forms for the right-hand D-glucopyranose unit. Decision on these three matters can be made readily if sucrose should ever be found to result from a partial hydrolysis of melezitose, because sucrose is almost certainly f)-v-fructo-... 

One notices that the data from the oxidation of melezitose by per-iodic acid confirm the pyranose structure of the D-glucose unit in turanose, and therefore also in the case of maltose, in agreement with the original assignments for both of these disaccharides from methylation studies. 

Fischer confirmed the disaccharide formulation for twranose by osazone formation (1894). Turanose is formed from the trisaccharide melezitose, which is fermentable with yeast. 

Following Tanret s6 discovery that turanose is a n-glucosyl-v-fructose, the possibility was widely recognized that melezitose might have the structure of a d-glucosyl-sucrose, as shown in formula I. 

One of the major points advanced by Kuhn and von Grundherr for the substituted-sucrose structure of melezitose was the extreme ease of acid hydrolysis of one of the linkages, which had earlier led Alekhine to the discovery of turanose and the trisaccharide nature of melezitose. For years this feature was accepted as virtual proof of the presence of sucrose in the melezitose molecule. However, the opinion that the ease of hydrolysis was evidence for the furanoid form of the D-fructose ring lost all validity with the discovery by Purves and Hudson1 that methyl D-fructopyranoside is hydrolyzed by acids with the same ease as methyl D-fructofuranoside moreover, the ease of hydrolysis never was evidence concerning the a- or /3-configuration of the D-fructose unit in melezitose. ... 

Fig. 3. >M—X-Ray diffraction patterns of melezitose, sucrose from melezitose, natural sucrose, and turanose. The diagrams were made by Mr. William C. White of the National Institutes of Health.

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