Carbohydrates, acidic derivatives solution

To model the moiety of glycoproteins which coimects the protein and carbohydrate parts of the molecule, amino acid - carbohydrate adducts (e.g. V-D-gluconylamino acids, thiazolidine-4-carboxylic acid derivatives of carbohydrates, " D-fructose amino acid derivates, etc.) have been synthetized. The protonation and metal ion (Cu2+, Ni2+, Co ", Zn2+ and Et2Sn2+) coordination equilibria of these model compounds have been studied by means of potentiometric equilibrium measurements. CD, EPR, NMR, EXAFS and MSssbauer investigations (the latter in frozen solutions) have been used to determine the structure and symmetry of the coordination sphere of the complexes. >6... 

In 1995 Nicolaou and coworkers initiated a renaissance in the construction of sugar amino acid conjugates with their synthesis of carbonucleotoids [49]. Although they did not prepare amide-linked carbohydrates, they did introduce the term carbopep-toid to designate such materials. Shortly thereafter, a number of papers directed toward the synthesis of carbopeptoids appeared. One of the earliest was reported by Wessel et al., who used nor-muramic acid derivatives and condensed them in solution by means of 2-chloro-4,6-dimethoxy-l,3,5-triazine (CDMT) in DMF to construct a tetramer (Fig. 27). 

Chiral ferroceneboronic acid derivatives have been synthesized by Ori and tested for chiral electrochemical detection of monosaccharides. The best discrimination was observed for L-sorbitol and L-iditol at pH 7.0 in 0.1 mol dm phosphate buffer solution. Moore and Wayner have explored the redox switching of carbohydrate binding with commercial ferrocene boronic acid. From their detailed investigations, they have determined that binding constants of saccharides with the ferrocenium form are about 2 orders of magnitude greater than those for the ferrocene form. The increased stability is ascribed to the lower pKe of the ferrocenium (5.8) than ferrocene (10.8) boronic acid. 

The degradation of carbohydrates by strong acids has been recognized for many years. It was a common elementary school demonstration to add sulfuric acid to sugar (sucrose) to produce carbon. Under more controlled conditions, the reaction of all carbohydrates in aqueous solution with strong acid has been shown to produce the formation of a derivative of furfural as the major product [7]. 

In the acid hydrolysis process (79—81), wood is treated with concentrated or dilute acid solution to produce a lignin-rich residue and a Hquor containing sugars, organic acids, furfural, and other chemicals. The process is adaptable to all species and all forms of wood waste. The Hquor can be concentrated to a molasses for animal feed (82), used as a substrate for fermentation to ethanol or yeast (82), or dehydrated to furfural and levulinic acid (83—86). Attempts have been made to obtain marketable products from the lignin residue (87) rather than using it as a fuel, but currently only carbohydrate-derived products appear practical. 

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