Of melezitose

Alekhine discovered the fully acetylated crystalline derivative of melezitose, the hendecaacetate, which has become of aid in the precise identification of melezitose. It crystallizes readily m. p. 117°, [oJd20 + 111° in benzene and +104° in chloroform (ref. 17). 

In 1918 Miss Helene M. Boas, of the New York Botanical Garden, sent to the writer a sample of manna which had been collected by James A. Teit near Spence s Bridge, British Columbia, from Douglas fir trees (Pseudotsuga taxifolia Brit., syn. P. Douglasii Carr.). The dry, white, crystalline manna (42.5 g.), in which some small stems and needles of the tree (4 g.) were encrusted, was entirely soluble in water and it proved to consist principally of melezitose.17 The authors stated that if the manna can be obtained in large quantities, which appears to be the case, it will indeed furnish an excellent source for melezitose. However, there was found within a few months by the same workers an abundant... 

A sample of melezitose was dissolved in an excess of water and filtered into a small beaker, which was covered with filter paper and allowed to stand at ordinary temperature for several days. The crystals which separated attained a diameter of a millimeter but were crowded together to such an extent as to make them unsuitable for crystallographic measurements. A few minute simple ones were picked out and the balance redissolved by addition of a little water and warming. The liquid was then allowed to cool and the crystals previously picked out were Tntroduced, the vessel being allowed to stand in a room kept at a constant temperature of 20° for several days. The same procedure was followed, using 50% alcohol as the solvent. 

In the same article28 Wherry describes the optical properties of melezitose as follows ... 

Refractive Indices of Melezitose for Different Wave Lengths... 

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-... 

The presence of the pyranose ring in the two D-glucose units of melezitose was inferred by Zempl6n and Braun from good evidence, and made certain by Miss Leitch29 through the crystallization of the requisite amount of 2,3,4,6-tetramethyl-D-glucose from the scission products of the fully methylated trisaccharide. The revised interpretation of Miss Leitch s experimental data concerns only the structure of the... 

Recent work by Richtmyer and the writer48 has confirmed this formula XV through a study of the oxidation of melezitose by per-iodic acid. They found that the oxidation resulted in the reduction of 4 moles of the acid to 4 moles of iodic acid for each mole of sugar, and the generation of 2 moles of formic acid no formaldehyde could be detected. It can be shown that these analytical measurements lead to this formula by an independent conclusive proof. 

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. 

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