Galactose methylated derivatives

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. 

For the properties of the methyl derivatives of 3,6-anhydro-L-galactose see Advances in Carbohydrate Chemistry, 2, 77 (1946).)... 

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... 

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 recent researches of Jeanloz6 have made available most of the (theoretically possible) methylated derivatives of 2-amino-2-deoxy-D-galactose. 

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. 

The basic principles concerned with the preparation of partially methylated derivatives of D-galactose and D-glucose are identical. Since Bourne and Peat1 have already provided a full discussion of these principles in connection with the latter sugar it would serve no useful purpose merely to re-enumerate their statements. It must be pointed out, however, that in the case of D-galactose, with only two exceptions, synthetic operations have always commenced with derivatives of the (1) E. J. Bourne and S. Peat, Advances in Carbohydrate Chem., 5, 145-190 (1950). 

The 2-methyl derivative of 6-desoxy-D-altrose has been prepared by Young and Elderfield in connection with their studies on digitalose the latter sugar was identified recently by Schmidt, Mayer and Distelmaier as 3-methyl-G-desoxy-D-galactose (3-methyl-D-fucose). Young and Elder-field started with the methyl 2-methyl-a-D-altroside of Robertson and Griffith,"" which is prepared readily from compound XLI, and, by trityla-tion and acetylation, converted it to the crystalline methyl 2-methyl-3,4-... 

The g.l.c. separation of various methylated derivatives of mannose, galactose, and glucosamine as their trimethylsilylated derivatives has been described using 0.3-0.4% OV 225 on Chromosorb that had been surface modified by a high molecular weight polyethylene glycol. Conditions have been found for the separation of the TMS ethers of arabinose, xylose, mannose, ot- and /3-glucose, fructose, sorbose, xylitol, mannitol, and sorbitol on Chromosorb W-NAW with 15% Carbowax 20M, and a g.l.c. method for the quantitative determination of trehalose as its TMS ether has been reported." ... 

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