Galactose tetraacetate

D-tnannose, and D-galactose tetraacetate in CDCI3 and of A -(a-D-xylopyranosyl) imidazole triacetate in CDCI3 in the absence and in the presence of acid and found that both steric factors and polar factors (reverse anomeric effect) are likely to be involved in determining the relative percentages of the two conformations at coti-formational equilibrium. The obtained results could in large part be accounted for by steric factors, but the operation of additional polar factors was also likely (Table 2.6). 

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. 

Conversion of sugar phenylhydrazones into olefinic azo-sugars on treatment with acetic anhydride and pyridine was shown by Wolfrom and co-workers (28) (The acetylated forms of the acyclic phenylhydrazones of D-glucose, D-mannose, and D-galactose readily lose the elements of acetic acid to yield 1-phenylazo-frans-l-hexenetetrol tetraacetate when treated with warm aqueous ethanol (28, 30). It is assumed that atmospheric oxygen partakes in this elimination reaction.) This is a special case of base catalyzed -elimination reactions of the type proposed by Isbell in 1943 ( 31), involving consecutive electron displacement (which actu-... 

Fig. 1.—Rates of Consumption97 of Lead Tetraacetate by the Methyl a-D-Pyrano-sides of Mannose (1), Galactose (2), and Glucose (3), in Glacial Acetic Acid (Temp. 20°).

Fig. 4.—Rates of Consumption13 of Lead Tetraacetate by Some Aldoses (1) D-Mannose, (2) i.-Rhamnose, (3) D-Altrose, (4) D-Allose, (5) D-Galactose, and (6) D-Glucose (Temp. 0°).

Zinner98 has studied the acetylation of D-ribose in pyridine solution with acetic anhydride at various temperatures. At 0° the pyranose tetraacetate is the sole product, but as the temperature at which acetylation is carried out is increased, the furanose isomer is also formed, the proportions of the two isomers formed at 100° being nearly equal. These findings parallel the earlier work by Schlubach and Prochownick99 in the D-galactose series. Zinner also observed that the acetylation of D-ribose with sodium acetate and acetic anhydride at higher temperatures gives rise to the furanose tetraacetate. 

D-Galactose methylphenyl-phenyl-osa-zone anhydride, III, 34 D-Galactose methylphenyl-phenyl-osa-zone tetraacetate, III, 34 D-Galactoae p-nitrophenylhydrazone, III, 26... 

D-Galactose phenylosazone anhydride and diacetate, III, 32, 33 D-Galactose phenylosazone tetraacetate,... 

Anomeric ediyl hemiacetals of the methyl ester of aldehydo-D-galacturonic acid tetraacetate were prepared by Dimler and Link. In chloroform, these isomers mutarotated to an intermediate value over a period of several hours, and the mutarotation was complex. Solvent-free oldehydo-D-galactose pentaacetate was obtained in crystalline form, and did not show mutarotation in 1,1,2,2-tetrachloro-ethane. " In the presence of water, the corresponding crystalline aldehydrols of aZde/tydo-D-galactose pentaacetate and aldehydo-T>-mannose pentaacetate were obtained. 

That migration of acetyl groups had not taken place during the formation of the D-galactose methylphenylhydrazone tetraacetates was shown by the isolation of two different p-toluene sulfonates from IX and X. This evidence shows therefore that even when oxide rings are present in (16) J. Compton and M. L. Wolfrom, J. Am. Ckem. Soc., 66, 1157 (1934). 

The discovery was made in 1936 that by deacetylating D-glucose phenylosazone and D-galactose phenylosazone tetraacetates at room... 

Osazone anhydrides have also been prepared by the deacetylation of the tetraacetates of n-galactose methylphenyl-phenylosazone and from... 

A new type of orthoester was reported by Wolfrom and Weisblat. The substance, designated l-thioethoxy-oide%do-D-galactose ethyl 1,2-orthoacetate 3,4,5,6-tetraacetate (XV), m. p. 125-126 and + 54 ,... 

Figure 4.11 Rise of absorption (A) at 400 nm after addition of Con A to bilayer vesicles with carbohydrate head groups. D-glucose and D-mannose head groups are precipitated as well as their tetraacetates. D-galactose and L-glucose vesicles remain in solution, both as free carbohydrates and tetraacetates. 0.01 mM OL-D-methylglucoside impedes the stereoselective action of Con A.

Next, the sugar portion sensitive to oxidation was protected by means of acetylation, and the penta-O-acetyl-n-galactose diphenylformazan was oxidized with lead tetraacetate. By the action of the calculated amount of the oxidant, penta-O-acetyl-n-galactose diphenyltetrazolium chloride CG.T.C. acetate) was obtained as characteristically shaped, colorless prisms upon addition of an appropriate quantity of hydrochloric acid. Owing to its ionic structure, this compound is quite soluble in water and is readily reduced to the corresponding acetylated formazan, which is red. Saponification of the penta-O-acetyl-D-galactose diphenyltetrazolium... 

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