Galactose configuration

Carbon number one of galactose (/ configuration) is linked to carbon four of glucose. Lactose is formed as a result of the process shown in Figure 9.17. 

Dehydration of D-fucose (9) to the enol (10) seems reasonable because D-fucose has the galactose configuration, i.e. an axial 4-OH group. D-Quinovose, which has a D-glucose configuration, might also be involved. 

Galactose differs from glucose in configuration at C-4. The C-4 hydroxyl is axial in p-D-galactopyranose, but it is equatorial in p-o-glucopyranose. ... 

The a anomers of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose have the same nir c.d. bands in 1 1 methanol-water at 0° as the anomeric mixtures have in aqueous solution. This indicates that the anomeric configuration has little influence on the nir c.d. band. 

The hypothesis could also account for differences in the relative sweetness of sugars by simple consideration of the way in which configurational differences might affect hydrogen bonding. The sweetness of D-galactose... 

The product retains, however, the configuration of D-galactose and is in fact methyl trimethyl-D-galactopyranoside (LII). The intermediate formation of a 1,3-anhydro ring is postulated. 

Neither has oxidation, with lead tetraacetate, of the sirup obtained by dehydration of the D-galactose condensate VIII so far resulted in isolation of the expected dialdehyde. On the other hand, when the anhydride from the D-glucose condensate (XXXIV) was oxidized with lead tetraacetate, an appreciable amount of dialdehyde (XXXVI) was isolated. This discrepancy in behavior is probably attributable to the trans position of the hydroxyl groups of the anhydride derived from D-galactose as compared with the cis configuration for the anhydride from D-glucose. 

Deoxygalactose (fucose) and arabinose both exist in Nature in d and l forms, and both are related in configuration to the corresponding galactoses. 

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