Turanose, structure

The reader is referred to the review article8 of Hudson for a thorough treatment of the development of knowledge of the turanose structure. 

In41 the foregoing proof of the structure of turanose, the generally accepted structure of maltose which has come from the evidence supplied... 

It has been assumed in the preceding section that the phenylosazones of turanose, maltose, and D-glucosyl-D-arabinose have structures like that of D-glucose pjienylosazone. This normal osazone structure is now proved40 by the following data for the turanose and maltose osazones, and there can be little doubt that it also holds for the osazone of d-glucosyl-D-arabinose. Turanose phenylosazone has been converted by... 

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. 

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. ... 

The pure enzyme displayed the preference sucrose > raffinose > 1-kestose > nystose (in a ratio 100 24 10 6). Other carbohydrates such as turanose, cellobiose, melibiose, leucrose, methyl-a-D-glucopyranoside, and stachyose were also tested but their activity was negligible. Thus, the enzyme only recognized sugars containing a sucrose moiety in their chemical structure. The trisaccharide raffinose is equivalent to a sucrose molecule substituted at the C-6 hydroxyl group, whereas... 

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