Galactose selective methylation

J. M. Williams and A. C. Richardson, Selective acylation of pyranosides I. Benzoylation of methyl a-D-glycopyranosides of mannose, glucose and galactose, Tetrahedron, 23 (1967) 1369-1378. 

M. W. Homer, L. Hough, and A. C. Richardson, Selective benzoylation of methyl 2-benzamido-2-deoxy-a-D-glucopyranoside A convenient preparation of derivatives of 2-amino-2-deoxy-D-galactose, /. Chem. Soc., Sect. C (1970) 1336-1340. 

Small-intestine lactase (GH 1), the absence of which is associated with lactose intolerance in a large proportion of the adult population, was probed with monodeoxy as well as selected mono-O-methyl derivatives in the galactose moiety of methyl lactosides.112 This enzyme required hydroxyl groups at C-2 and also C-3, while neither the presence of a 4-OH group nor a specific configuration at C-4 was prerequisites for successful hydrolysis. A 6 -deoxy lactoside was readily hydrolyzed, but the absence of 6-OH in the gluco moiety caused it to be a poor substrate. 

N. O. Maness, J. D. Ryan, and A. J. Mort, Determination of the degree of methyl esterification of pectins in small samples by selective reduction of esterified galacturonic acid to galactose, Anal. Biochem., 185 (1990) 346-352. 

In like fashion, by careful stereochemical correlation of the three masked hydroxy stereocentres in 4 [i.e. C(13), C(14) and C(15) using FK506 numbering] with various monosaccharide derivatives (Scheme 17.3), Danishefsky was able to establish an appropriate chirality match with the C(2), C(3) and C(4) stereocentres of D-galactose. Methyl p-D-galactopyranoside was therefore selected as the starting material for his synthesis of 4. 

It should be noted that, during methylation, there is a selective loss of hemicellulose rich in galactose residues.148 In most studies on hemicelluloses, the materials extracted from holocellulose by alkali are recovered by mild acidification, followed by addition of an excess... 

The chief chemical use of such nitrates has arisen from opportunities to take advantage of their stability, the easy, selective removal of the nitrate groups from certain positions, and their ready and complete denitration by reductive processes. These properties have permitted preparation of several new methyl ethers of D-glucose, D-galactose, and D-fructose. ... 

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