Maltose reaction with amino acids

Chemists have demonstrated that maltol may be formed (1) by heating maltose at3758 F (191 C) for 1 hour (note the similarities of these conditions to those in baking), or (2) by heating mixtures of sugars, such as maltose and lactose, with amino acids, such as glycine (the latter procedure is known as nonenzymatic browning reaction of the Maillard type). 

Chromatographic batch reactors are employed to prepare instable reagents on the laboratory scale (Coca et al., 1993) and for the production of fine chemicals. These applications include the racemic resolution of amino acid esters (Kalbe et al., 1989), acid-catalyzed sucrose inversion (Lauer, 1980), production of dextran (Zafar and Barker, 1988) and saccharification of starch to maltose (Sarmidi and Barker, 1993a). Sardin et al. (1993) employed batch chromatographic reactors for different esterification reactions such as the esterification of acetic acid with ethanol and the transesterification of methylacetate. Falk and Seidel-Morgenstern (2002) have investigated the hydrolysis of methyl formate. 

Fig. 3. Substrate binding site on Taka-amylase A deduced from electron density difference maps with the enzyme-maltose complex and model building. The seven saccharide binding sites are numbered. Presumed catalytic amino acids Asp-206 and Asp-297 surround the sessile glycoside bond. Glu-230 is considered as a possible catalytic amino acid as well because of its proximity to the reaction center. Adapted from Matsuura et al. (262) with permission from J. Biochem (Tokyo).

Seibel et al. [36] reported, for the first time, the use of microwave heating in the glycosylation of amino acids. They performed glycosyl transfer reactions of perace-tylated monosaccharides (glucose and galactose) and disaccharides (maltose and lactose) with N-9-fluorenylmethoxycarbonyl-L-serine benzyl ester in the presence of iron trichloride with short reaction times (4 min, compared with 5-10 h by conventional heating) and with improved yields (52-61% compared with 10-31% by conventional heating). It is worthy of note that in these reactions heavy metal compounds, for example silver trifluoromethanesulfonate, mercury dibromide and di-cyanide, or boron trifluoride-diethyl etherate, can be replaced by the environmentally safe promoter iron trichloride. 

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