Aqueous Solution Substituted and Derived Sugars

Composition in Aqueous Solution Substituted and Derived Sugars 

Whereas the composition of solutions of the unsubstituted aldoses and ketoses has been systematically investigated, very few studies have been conducted on substituted and on derived sugars, such as amino sugars, 

In particular instances, the increased interactions can be clearly defined. Three examples will be considered. The equilibrium composition of 3-O-methyl-D-fructose at 16.5° was found112 to be 18 37 11 34, compared to 2 70 5 23 for d-fructose at 30°. In the -pyranose, which assumes the 2Cs(d) conformation (16), the methyl group has a 1,3-paral- 

The composition of a solution of 3-O-methyl-D-psicose15 at 27° is 31 7 56 6, whereas that of D-psicose is 22 24 39 15. In this case, the methoxyl group in the / -pyranose form (17) is axial, and 1,3-parallel interaction with one of its equatorial neighbors cannot be avoided. There is a similar interaction in the / -furanose form, too, but not in the a anomers. 

There is also an axial methoxyl group flanked by two equatorial hydroxyl groups in both of the pyranose forms of 3-O-methyl-D-allose. The pyranose forms are thereby destabilized, and, in solution, the proportions of the furanose forms are more than doubled,88 to give the composition 14 65 7.5 13.5 at 31 °. 

Another example of substitution increasing the ratio of a- to / -pyranoses [p. 45] is 3-O-methyl-D-altrose46 25% a- and 32% /J-pyranose, 43% a + fi-furanose. 

Fructoses O-substituted by glucosyl in various positions are discussed in Section V,l. 

The presence of substituents outside the ring usually does not affect the composition. Thus, D-allose 6-phosphate, D-altrose 6-phosphate, and d-manno-heptulose 7-phosphate have practically the same composition as the parent sugars.51 

4-Amino-4,6-dideoxy-D-mannose hydrochloride (perosamine) forms an — 45 55 mixture of the a- and / -pyranose forms in solution.52 For 2-amino-2,6-dideoxy-D-glucose 6-sulfonic acid, the a / pyranose ratio is 68 32 at 20°, indicating [p. 47] that, in solution, the sugar is zwitterionic.53 

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VI. Composition in Aqueous Solution Substituted and Derived Sugars. 42... 

Grollmann U, Schnabel W (1980) On the kinetics of polymer degradation in solution, 9. Pulse radiolysis of polyethylene oxide). Makromol Chem 181 1215-1226 Hamer DH (1986) Metallothionein. In Richardson CC, Boyer PD, Dawid IB, Meister A (eds) Annual review of biochemistry. Annual Reviews, Palo Alto, pp 913-951 Held KD, Harrop HA, Michael BD (1985) Pulse radiolysis studies of the interactions of the sulfhydryl compound dithiothreitol and sugars. Radiat Res 103 171-185 Hilborn JW, PincockJA (1991) Rates of decarboxylation of acyloxy radicals formed in the photocleavage of substituted 1-naphthylmethyl alkanoates. J Am Chem Soc 113 2683-2686 Hiller K-O, Asmus K-D (1983) Formation and reduction reactions of a-amino radicals derived from methionine and its derivatives in aqueous solutions. J Phys Chem 87 3682-3688 Hiller K-O, Masloch B, Gobi M, Asmus K-D (1981) Mechanism of the OH radical induced oxidation of methionine in aqueous solution. J Am Chem Soc 103 2734-2743 Hoffman MZ, Hayon E (1972) One-electron reduction of the disulfide linkage in aqueous solution. Formation, protonation and decay kinetics of the RSSR radical. J Am Chem Soc 94 7950-7957... 

The application of indium- and tin-mediated Barbier-Grignard reactions in aqueous solution to the chain extension of unprotected sugars has been reviewed. Some C-5 variants of iV-acetylneuraminic acid have been prepared by the indium-mediated addition of ethyl oc-(bromomethyl)acrylate to variously N-substituted mannosamines," and similar chemistry using (bromomethyl)vinyl phosphonate has led to the phosphonate analogue 12. The reaction of O-protected aldono-1,4- and -1,5-lactones with (2-bromomethyl)-acrylate or -acrylonitrile or 2-bromobutyrolactone mediated by samarium diodide led to chain-extended ulosonic acid derivatives." ... 

Heating dihydroxyacetone in aqueous solution at pH 5 produced a complex mixture containing substituted pyranones, dipyranones, substituted quinones, hydroxylated benzenes and toluenes, and the sugar derivatives (3), (4), and (5). The syntheses from telomerization of vinylene carbonate of racemic o-glycero-L-gulo f D-g/ycero-D-irfo-heptose, and v-threo-D-ido-octose in reasonable yield has been reported. ... 

Although the sugars condense with nitromethane in aqueous alkali (148a), the reaction usually is carried out in methanol solution (or suspension) with sodium methoxide acting as the basic catalyst. In the most favorable examples of the condensation reaction, the sodium salts of the C-nitroalco-hols precipitate from this solution and can be isolated simply by filtration. As in the cyanohydrin condensation, two epimeric products are formed, usually in unequal amounts. After removal of the sodium by ion exchange, the epimeric (7-nitroalcohols frequently can be separated by fractional crystallization. For some syntheses, partially substituted sugars, such as the benzylidene derivatives, may be used to advantage. 

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