Galactose structure

The antibacterial activity of 50 units of streptomycin per milliliter toward S. aureus was suppressed by 0.0002 milligram of lipositol per milliliter. The observers of this interesting phenomenon pointed out that the presence in lipositol of an inositol-galactose structure suggested the possibility of a metabolite-antimetabolite relationship with streptomycin. 

Suckfull (88) in their establishment of the 1,6 or septanose ring form in the i -D-galactose structure. 

UDP-Glc is converted into UDP-Gal by a reaction catalyzed by UDP-Gal-4-epimerase. The enzyme is NAD dependent and the first reaction that it catalyzes is the oxidation of C-4 of UDP-Glc to give the 4-keto intermediate and NADH. The complex undergoes a conformational change and the NADH-product stereospecifically reduces the keto group to give the D-galactose structure [13-15] (see Fig. 10.6). 

D-galactose, C HiiOe. Crystallizes in the pyranose form m.p. 1I8-120 C (monohydrate), 165-5" C (anhydrous). An isomer of glucose which is fairly widely distributed in plants. It is a constituent of raffinose and slachyose, of hemicelluloses, of pectin, of gums and mucilages, and of some glycosides. In animals it forms half the lactose molecule and is the sugar found in the brain. Chemically it is very similar to glucose. It has the structure... 

Write structural formulas for the a and 3 methyl pyranosides formed by reaction of o galactose with methanol in the presence of hydrogen chloride... 

Sucralose has the structure most similar to su crose Galactose replaces the glucose unit of sucrose and chlorines replace three of the hydroxyl groups Sucralose is the newest artificial sweetener having been approved by the U S Food and Drug Adminis tration in 1998 The three chlorine substituents do not dimmish sweetness but do interfere with the ability of the body to metabolize sucralose It there fore has no food value and IS noncaloric... 

The structure of compound A was established in part by converting it to known compounds Treat ment of A with excess methyl iodide in the presence of silver oxide followed by hydrolysis with dilute hydrochlonc acid gave a tnmethyl ether of D galactose Companng this trimethyl ether with known trimethyl ethers of D galactose allowed the structure of compound A to be deduced... 

Draw the structure of i.-galactose, and then answer the following questions ... 

Deoxy-sugars. Part XXV. Structure and Reactivity of Anhydro-sugars. Part II. Derivatives of 3 6-Anhydro-D-mannose, 3 6-Anhydro-2-deoxy-D-galactose, and 3 6-Anhydro-2-deoxy-D-g ucose," A. B. Foster, W. G. Overend, M. Stacey, and G. Vaughan,/. Chem. Soc., (1954) 3367-3377. 

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