Stachyose methylated

Fig. 1.—Molecular-rotation relationships of several raffinose-type oligosaccharides. Me, methyl a-D-galactopy ranoside Gl, D-glucose Mb, melibiose Mt, manninotriose Vt, verbascotetraose S, D-glucitol M, melibiitol Ml, manninotriitol Su, sucrose K, raffinose St, stachyose V, verbascose Gb, gentiobiose Ge, gentianose.

As part of his monumental study20 on stachyose, Onuki converted manninotrionic acid into its completely methylated derivative, which he hydrolyzed, to obtain methylated D-galactoses and methylated D-gluconic acid. These products were isolated and identified by Onuki as 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,4-tri-O-methyl-D-galactose and 2,3,5,6-tetra-O-methyl-D-gluconic acid. From these findings, Onuki proposed that manninotriose is... 

Recently, Laidlaw and Wylam reported27 the complete methylation analysis of stachyose (see the following Section). Their results, likewise, require a 1,6 linkage between the D-glucose and D-galactose units. 

Methylation of stachyose and subsequent hydrolysis, by Onuki,20 gave 2,3,4,6-tetra-O-methyl-D-galactose (identified as the crystalline anilide), a tri-O-methyl-D-galactose and a tri-O-methyl-D-glucose (which were converted into the 2,3,4,6-tetra-O-methyl derivatives, and characterized as the crystalline anilides), and 1,3,4,6-tetra-O-methyl-D-fructose, a sirup which agreed in properties with the authentic material. 

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... 

The powdered-cellulose, chromatographic assay of the hydrolyzate of methylated stachyose has furnished important structural data. 1,3,4,6-Tetra-O-methyl-D-fructose, 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,4-tri-0-methyl-D-galactose, and 2,3,4-tri-O-methyl-D-glucose were recovered in approximately equimolar quantities the glycosidic 1- 6 bond for the D-glucose residue and for one of the o-galactose residues in stachyose is clearly indicated. 

The synthesis of methyl 0- -D-galactopyranosyl-( 1 ->-6)-(7-ci -D-galactopyrano-syl-(l->6)-0-a -D-galactopyranosyl-(l ->-6)-0-jS-D-glucopyranoside from stachyose has been reported. ... 

Structure. Cryoscopic molecular weight values indicate that verbascose is a pentasaccharide 169). From methylation studies, Murakami concluded that verbascose was a D-galactosyl-substituted stachyose (at C-6 of the terminal D-galactose unit of stachyose). Hot dilute acetic acid removes the D-fructose unit from verbascose to give a tetrasaccharide verbascotetraose (m.p. 240°C. [a] +191.4 (water)). This tetrose has been partially hydrolyzed, with removal of D-glucose, to give the crystalline trisaccharide galactotriose 164)-... 

Fatty acid polyesters have been prepared by the weU established method of transesterification in the presence of sodium metal from the peracetates of D-glucitol and trehalose, of methyl glucoside, methyl galactoside, octyl glucoside, and stachyose, and of sucrose. The process for formation and purification of sucrose polyesters has been optimised to furnish pure products in >99% yield. ... 

The enzymatic hydrolyses (as just indicated) give the basic structure of stachyose and raffinose. The only remaining question is the ring size of the first galactose unit of stachyose. That methylation of stachyose and subsequent hydrolysis yields 2,3,4,6-tetra-O-methyl-D-galactose establishes that this ring is a pyranoside. 

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