Manninotriose

Synthesis of melibiose Isolation of manninotriose, stachyose (manneotetrose) from ash manna correct molecular formula for Fischer 1902 13... 

A comparative study of the action of yeast invertase on sucrose, raffinose, and stachyose was reported by Adams, Richtmyer and Hudson (see Table V).23 Hydrolysis by invertase has been found to give D-fruc-tose, in each case, and the complementary aldose D-glucose, melibiose, or manninotriose. In general, the same products are formed as in mild acid hydrolysis. 

Synthesis of manninotriose and a higher oligosaccharide,33 by trans-galactosylase action of yeast melibiase on melibiose, has already been noted in a preceding paragraph. 

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.

Manninotriose is known chiefly as a product of partial acid hydrolysis, or invertase hydrolysis, of stachyose, although it occurs14 in free form,... 

In his preparation of manninotriose from crystalline stachyose, Onuki followed the procedure worked out by Tanret, and obtained a product with somewhat higher optical rotation [a]26n + 174.57° (c 0.5, in water). 

Manninotriose (0.8 g.) was heated with 1.44 g. of phenylhydrazine hydrochloride, 0.22 g. of o-phenylenediamine, and 0.5 g. of glacial acetic acid in 20 ml. of water at 100° in a stoppered tube. After 3 hours, the reaction mixture was cooled and neutralized with 40 ml. of 0.5 N sodium hydroxide. The trisaccharide flavazole was isolated by fractional extraction of the solution with ether (to remove organic bases and colored impurities), ethyl methyl ketone (to remove traces of monosaccharide and disaccharide flavazoles, as well as other colored impurities), and butanol (which extracted the trisaccharide flavazole). Each step in the fractionation process was followed by... 

Manninotriose can be reduced by Raney nickel or by sodium boro-hydride to give manninotriitol, perhaps the most useful manninotriose derivative. French and associates found28 that manninotriitol crystallizes with exceptional ease from a solution in methanol, and, after recrystallization from that solvent, gives fine tufts of needles of m. p. 190-1°, [a]28D + 147° (c 2, in water). 

From the structural point of view, manninotriose has been of critical significance in relationship to its parent tetrasaccharide, stachyose. Almost invariably, structural studies on manninotriose have gone hand-in-glove with complementary studies on stachyose. 

The molecular size and the sequence of monosaccharide units in manninotriose was clear to Tanret.14 He showed that oxidation of manninotriose by bromine gives an acid which, on hydrolysis, gives D-gluconic acid and D-galactose. 

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... 

Thus, the preponderance of evidence indicates that manninotriose... 

The enzymic synthesis of manninotriose from melibiose is mentioned in Section II-4. 

It is to be hoped that the application of newer methods of preparation and purification will make manninotriose more accessible to the research worker, so that this structurally well-characterized oligosaccharide can be exploited for use in further physical, chemical, and biochemical investigations. 

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