Of sugar acetates

Molecular ion Chemical ionization using ammonia as reagent gas establishes the molecular weights of sugar acetates. 

The Hines64 showed that, as acids, ethanol, isopropyl alcohol, and tert-butyl alcohol are weaker than water, whereas methanol is stronger. The influence of the solvent could thus be interpreted in terms of equation 1. In methanol, the equilibrium would be more displaced to the right, and the rate of simple ammonolysis and transesterification would be enhanced, with concomitant decrease in the yields of amido sugars. In water (for the ammonolysis of sugar acetates) and in alcohols other than methanol, the equilibrium would be displaced to the left and this would allow operation of the orthoester mechanism a better chance. The isolation, from the reaction in isopropyl alcohol, of mono-O-benzoylated bis(benzamido)alditols, could also be explained on this basis. 

In the early 1920 s, while attempting to obtain the sodium salt of n-glu-cose, with the cooperation of Alfons Kunz, he discovered a new process for the catalytic saponification of sugar acetates, using sodium methoxide, a method which has now become a standard procedure. The process was modified and somewhat improved later, with the assistance of Eugen Pacsu and Arpad Gerecs. 

Further Experiments on the Oxidation of Sugar Acetals and Thioacetals by Aceto-bacter suboxydans, D. T. Williams and J. K. N. Jones, Can. J. Chem., 45 (1967) 741-744. 

Bonner has measured the rates of anomerization and the equilibrium constants for a number of sugar acetates (see Table XVI) and has suggested that the reactivity sequence supports a bimolecular mechanism. Actually, this sequence is very similar to that obtained for the solvolyses of poly-0-acetylglycosyl halides (see Table XIV), which are known to proceed by a unimolecular mechanism. Bonner s results would seem, therefore, to be more in accord with a unimolecular mechanism for the anomerization. 

Concerning the mechanism of the rearrangement of sugar acetates by aluminum chloride, there is very little to be added at the present time. The reaction proceeds equally as well with the a-octaacetate of cellobiose as it does with the /3-octaacetate of lactose.Under the most favorable conditions so far discovered, it appears that octaacetyl-lactose is converted to about equal amounts of acetochlorolactose and acetochloroneolactose similar results were obtained with octaacetyl-cellobiose. Although Kunz and Hudson believed acetochlorolactose to be the primary reaction product, which was transformed subsequently to the isomeric neolactose derivative, later experiments by Richtmyer and Hudson did not substantiate this view. In an uncompleted study of the action of a mixture of aluminum and phosphorus chlorides upon pentaacetyl-D-glucose, Richtmyer and Hudson have demon.strated that both D-altrose and n-mannose derivatives are formed by rearrangement of the D-glucose molecule. 

During a study devoted to fragmentation of sugar acetals in the presence of butyllithium [142], the formation of unsaturated pyranoses (36-38) from L-rhamnose derivative 35 was observed and explained in terms of anionic species rearrangement (O Scheme 12). 

Fregapane, G., Sarney, D. B., and Vulfson, E. N., Enzymic solvent-free synthesis of sugar acetal fatty acid esters. Enzyme Microb. Technol., 13, 796-800, 1991. 

This process is the main course for the acid-catalyzed anomerization of sugar acetates, methyl glycosides, and related compounds in non-aqueous solvents.104,244,245 260,263 In many instances, formation of the cyclic carbonium ion is assisted by participation of a neighboring acetyl group,104 but this process is not a necessary feature. Anomerization of tetra-O-acetyl-2-deoxy-a-D-arafomo-hexopyranose takes place through a cyclic carbonium ion as depicted.245[Pg.43]

A Polymer-homologous Series of Sugar Acetates from the Acetolysis of Cellulose, E. E. Dickey and M. L. Wolfrom,/. Amer. Chem. Soc., 71, 825-828 (1949). 

Chromatography of Sugar Acetates and Methyl Ethers on Magnesol, M. L. Wolfrom, Rosa M. de Lederkremer, and L. E. Anderson, Anal. Chem., 35,1357-1359 (1963). 

Eerrer P, Montesinos JL, Valero E et al. (2001) Production of native and recombinant lipases by Candida rugosa a review. Appl Biochem Biotechnol 95 221—255 Fregapane G, Samey DB, Vulfson EN (1991) Enzymic solvent-free synthesis of sugar acetal fatty acid esters. Enzyme Microb Technol 13(10) 796-800 Fuenzalida M, Markovits A, Martinez I (2006) Process for producing sterol or stand esters by enzymatic transesterification in solvent and water free media. EP 1285969 Bl. Issued on November 10, 2006... 

Klemer and Kohla have reported further remarkable transformations of sugar acetals on treatment with alkyl lithium reagents. 1,6-Anhydro-D-galactose derivative (38) gave the cyclitol (39), In 85% yield for R=Bu, while the 1,6-anhydro-D-mannose derivative (ll0)... 

Kuribayashi T, Ohkawa N, Satoh S (1998) AgOTfa/SnCL a powerful new promoter combination in the aryl C-glycosidation of a diverse range of sugar acetates and aromatic substrates. Tetrahedron Lett 39 4537-4540... 

The production of various hydrazones of sugars acetic acid solution has been described. ... 

Fig. 229. Separation of sugar acetates according to Tate and Bishop [54] double development (17 cm runs) on silica gel G layer using benzene-methanol (96 + 4).

Table 210. Chromatography of sugar acetates on silica gel G thin-sulfoxide as stationary phase [60]...

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