E-Galactan

Only one other naturally occurring galactan has been examined in any great detail this is the e-galactan of the larch.40 It contains D-galacto-... 

Although pectic materials are known to be present in wood, it is not clear whether this e-galactan is a component of wood pectin, and in view of the wide difference in structure between this galactan and the one associated with pectin in lupin seeds, further investigations of this point will be awaited with special interest. 

Fig. 12.—Repeating unit of e-Galactan (possible formula) after E. V. White.

The most detailed structural studies to date have been carried out on the arabinogalactans or e-galactans from Western120-124 and European 26-127... 

The first structural study of the arabinogalactan or e-galactan from European larch was carried out by Campbell, Hirst, and Jones,126 who showed the polysaccharide to contain residues of D-galactose and L-arabinose in the proportion of 6 1. Fractionation of the methylated polysaccharide gave, as the main component, a methylated galactan containing... 

Further knowledge of the detailed structure of European-larch e-galactan has come from later investigations.126 127 In these studies, however, no evidence could be found for heterogeneity of the type previously encountered in the methylated derivative, and the e-galactan itself was ultracentrifugally homogeneous. 

In agreement with the earlier findings,126 approximately equimolecular proportions of 2,3,4,6-tetra-, 2,3,4-tri-, and 2,4-di-O-methyl-D-galacto-pyranose were isolated as the main products of hydrolysis of methylated e-galactan, but, in addition, small proportions of 2,3,4-tri-O-methyl-L-arabinose, 2,5-di-O-methyl-L-arabinose, and 2,4,6-tri- and 2-mono-0-methyl-D-galactose were found. Evidence in favor of partial structure XLI for the galactan framework was obtained by application to the polysac-... 

Lactose, phenylosotriazole, III, 38 a-Lactose, acetochloro-, I, 40, 41 Lactyl chloride, acetyl-, III, 367 Laminarin, IV, 275, 282 Langenbeck s formulation of enzymatic glycoside hydrolysis, V, 58 Larch, e-galactan of, II, 249 Larch manna. See Manna. 

Arabopyranose Residues in Larch e-Galactan, J. K. N. Jones, Chem. Ind. (London),... 

Isolated from partial acid hydrolysates of Virgilia oroboides, Anogeissus schimperi, Prunus persica, Opuntia ficus-indica (Indian fig) gums and Larix decidua e-galactan and Larix laricina arabogalac-tan. Needles (MeOH aq.). 

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