Fructose dicarbonyl compounds

Another class of pyrrole derivative may be obtained by the interaction of l-amino-l-deoxy-2-ketoses or 2-amino-2-deoxyaldoses with a jQ-dicarbonyl compound. Unlike the previous type (which is N-substituted), these pyrrole derivatives have a tetrahydroxybutyl group in the a- or /8-position with respect to the nitrogen atom of the ring, in addition to other groups arising from the dicarbonyl compound used in the condensation. The formation and reactions of this type of pyrrole derivative have been discussed in detail in two articles in this series48,49 they will, therefore, only be treated briefly. 1-Amino-l-deoxy-D-fructose (53) reacts with 2,4-pentanedione to give50 pyrrole derivative 54a similar pyrroles were obtained with ethyl acetoace-tate,50,51 which yields 54b. 

Problem 22.12 Osazones are converted by PhCHO to 1,2-dicarbonyl compounds called osones. Use this reaction to change glucose to fructose. 

Monosaccharides react with a variety of 1,3-dicarbonyl compounds in the presence of zinc chloride in ethanolic or aqueous solution to yield substituted furans (Scheme 69) (56MI31200). The reaction of ethyl acetoacetate with D-glucose and D-mannose yielded the trisubstituted furan (252) in 20% yield, while D-fructose under similar conditions yielded (253 7%). These products have been used for the synthesis of dehydromuscarones (63HCA1259). Oxidation of the tetrahydroxybutyl side chains with lead tetraacetate gives the aldehyde, which can be converted to the corresponding acid with alkaline silver oxide. 

Because a-dicarbonyl compounds are particularly reactive, Weenen and Apeldoom57 specifically looked for these compounds by means of derivatisation with o-diaminobenzene among the butanol-soluble fragmentation products formed in 15 systems (glucose, fructose, xylose, 3-deoxyglucosone, or fructosylalanine without amine or with alanine or cyclohexylamine 1 h, 100 °C, phosphate buffer, pH 8). Four a-dicarbonyls were obtained glyoxal, 2-oxopropanal, butanedione, and 2,3-pentanedione. 

The reaction of 1-amino-l-deoxy-D-fructose with /3-dicarbonyl compounds in aqueous acetone at neutral pH has also been studied. The acetate of this amino sugar affords, with ethyl acetoacetate, ethyl 2-methyl-4-(D-om6wo-tetrahydroxybutyl)pyrrole-3-carboxylate (17). As in previous... 

Alkylamino-l-deoxy-D-fructoses (32, R = n-C4H9, CHaCOjCaHs, CHaCeHs) react with the same dicarbonyl compounds giving the corresponding A-alkylpyrroles (33, R = ri-C4H(, (ilHaCOaCsHs, CHaCeHa R = OCaHa, Similarly, 1-arylamino-l-deoxy-D-fructoses (32,... 

Substances of structures (105) and (106) may be intermediates in the Amadori rearrangement of glycosylamines (104) when this reaction is catalyzed by certain /3-dicarbonyl compounds. Hydrolysis of (106) would give the products of the rearrangement, the V-substituted 1-aniino-l-deoxy-D-fructoses (109). Hodgehas obtained some evidence for the existence of intermediate compounds in the Amadori rearrangement he formulated these as the branched-chain amino ketoses (78, X = iV-alkyl or V-aryl). 

The amount of acrylamide formed in the reaction mixtures containing a-hydroxycarbonyl compounds, such as glucose, fructose or hydroxyacetone (acetol), is generally much higher than in the case of a-dicarbonyl compounds represented, for example, by butane-2,3-dione (biacetyl) or 2-oxopropanal (methylglyoxal) and other substances. It should also be noted that trace amounts of... 

Oxidation is facilitated by a neighbouring carbonyl group which stabilises the initially formed carbon-centred carbohydrate radical. The experimental order of reactivity was acetoin>hydro acetone>>D-gluconic acid > standard ketohexoses>> standard aldopentoses>standard aldohexoses>D-glucitol D-fructose and L-sorbose gave dicarbonyl compounds as the primary products and aldopentoses furnished aldotetroses. ... 

We conclude that dicarbonyl compounds are present in retail cola drinks. Cola drinks have markedly higher dicarbonyl contents when sweetened with high fructose com symp than with sucrose. Previous estimates of glyoxal, methylglyoxal and 3-DG in similar drinks in the USA were 10 - 100 fold, 10 - 30 fold and 3-10 fold higher, respectively, than estimates herein. Heating and non-acidic conditions in sample processing may have contributed to these apparent marked overestimates. 

By reaction of serine or phenylalanine with fructose instead of glucose we got identical results with the exception of higher pyra-zine concentrations (more than 50 % relatively higher ). Main products have been 2,5 and 2,6-dimethylpyrazine which may be formed via the reaction of two C,-dicarbonyls each. In our opinion these results demonstrate a specialise of fructose to decompose by chain cleavage. As another decomposition product of fructose we have identified furfurylalcohol after heating a reaction mixture at 120° C. Obviously this Cg-compound has been formed after cleavage of the carbon atom 1 from the sugar molecule. 

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