Glucosylamine A-

Figure 13. Formation of glucosyl-n-butylamine and glyoxal dialkylimine during the reaction of glucose (0.25 MJ with t-butylamine (1 MJ in ethanol. Key 0, glucosylamine A, imine 9, browning.

Crystalline samples sometimes produce spectra with distorted band shapes, an effect known as the Christiansen effect [see Potts (1963) and Table 1.4]. Also, polymorphic forms of the same substance frequently show differences in infrared spectra. An example is N-benzoyl-2,3,4,6-tetra-0-benzoyl- -D-glucosylamine, a compound that exists in a form with melting point 113-115°C which, when heated to 117-120°C and allowed to crystallize from the melt, gives a form with melting point 184°C having a somewhat different spectrum in Nujol (Tipson, 1968). Also, different crystal habits (same melting point) of a compound may display partially differing spectra, especially if examined as mulls, in which little pressure is applied. Shifts of up to 20 cm" for certain bands have been observed (Barker et al., 1956) for crystalline and amorphous forms of some carbohydrates. In all such instances, however, spectra of samples of each of the forms, recorded after dissolution in the same solvent, or as a molten substance, are identical. 

Glucoseptanose a-D-form , 1,2-0-Isopropylidene, 3,4,5-tri-Ac, G-521 Glucosyl isocyanide p-D-Pyranose- /brm, G-532 Glucosylamine p-D-Pyranose-/orw A-(4-Hydroxyphenyl), G-533 Glucosylamine a-D-Pyranose-/< rw A-(4-Methylphenyl), 2,3,4,6-tetra-Ac,... 

A stable enzyme-D-glucose intermediate has been obtained in the hydrolysis of methyl a-D-[ C]glucopyranoside by an a-D-glucosidase from Saccharomyces oviformis Phenol was used to terminate the reaction and to trap the intermediate in a rapid-flow technique. The intermediate appears to be covalently linked, since continuous washing of the denatured protein failed to remove the radiolabel, which was also retained by a tryptic peptide isolated by gel filtration. Treatment of the intermediate with acid released D-[ C]glucose. The radiolabel was not bound when the enzyme was replaced with bovine albumin or when jS-D-glucosylamine (a potent inhibitor of a-D-glucosidase) was added with the enzyme. 

The rate constants kr and k2 have values of 20 X 10-3 and 22 X 10-3 min-1, respectively, in 2 M hydrochloric acid at 100°, and the overall rate of decomposition of 2-acetamido-l-N-/3-L-aspartyl-2-deoxy-/3-D-glucosylamine occurs with a rate constant of 42 X 10-3 min-1, that is, a half-life of the order of 17 minutes.92 L-Aspartic acid and ammonia are released at the same rate.92-95... 

An experiment whose results support certain mechanistic views (see Section VI, p. 110) was the ammonolysis of 2,3,4,6-tetra-O-benzoyl-D-glucopyranosylamine,30 which afforded a mixture of D-glucose and D-glucosylamine in 95% yield, and only 1.4% of l,l-bis(benzamido)-l-deoxy-D-glucitol (17) with traces of N-benzoyl-D-glucopyranosylamine. 

For the N-acylaldobiosylamines, this method requires a second oxidation and further reduction, as shown for N-acetyl-6-O-a-D-galactopyranosyl-/3-D-glucosylamine (N-acetyl-/3-meIibiosylamine)49 (54) in the following sequence. 

As we stated previously, glucose forms some, but not all, of the common carbonyl derivatives. The amount of free aldehyde present in solution is so small that it is not surprising that no hydrogen sulfite derivative forms. With amines, the product is not a Schiff s base but a glucosylamine of cyclic structure analogous to the hemiacetal structure of glucose, Equation 20-3. The Schiff s base is likely to be an intermediate that rapidly cyclizes to the glucosylamine ... 

Another possible mechanism7 for the transformation of sugars with amino acids into colored products is through the Amadori rearrangement,44 which is the isomerization of an aldosylamine to a ketose derivative, for example, of a D-glucosylamine derivative to a derivative of 1-amino-l-deoxy-D-fruc-tose. Such a conversion has been shown to occur when an amino acid reacts... 

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