Anomers, differentiation

Table 6.5. Anomer-Differentiating Bands, in cm Shown by Four Methyl Pyranosides (Tipson and Isbell, 1960b)...

Inouye M (1976) Differential staining of cartilage and bone in fetal mouse skeleton by alcian blue and alizarin red S. Cong Anom 16 171-173... 

Carbohydrates in nature are optically active and polarimetry is widely used in establishing their structure. Measurement of the specific rotation gives information about the linkage type (a or (3 form) and is also used to follow mutarotation. Nuclear magnetic resonance spectroscopy (NMR) can be used to differentiate between the anomeric protons in the a- or /3-pyranose and furanose anomers and their proportions can be measured from the respective peak areas. 

Free 4-acetamido-4,5-dideoxy-D (or L)-xylose is a syrup, and its infrared spectrum shows negligibly small bands for the imino and carbonyl groups. The syrup consists of two components, present in about equal amounts, - that are chromatographically separable. They yield the same (2-benzyl-2-phenyl)hydrazone, and are interconvertible by acid catalysis. Their optical rotations and their nuclear magnetic resonance spectra show that they are anomeric forms - of 195. Their nuclear magnetic resonance spectra are differentiated by the positions of the signals for their H-1 protons (t 4.72 and 4.84). The spectrum of each anomer shows, on acidification, a rapid attainment of anomeric equilibrium. A... 

Alumina " is an excellent adsorbent for the chromatography of certain sugar derivatives. It sharply differentiates between anomers, yielding crystalline substances from both sirupy and crystalline mixtures. Frequently, the 13-d anomer moves down the adsorbent column more rapidly than does the a-n form 1,2,4-tri-0-acetyl-6-deoxy-3-0-methyl-d-D-glu-... 

Functionalized monosaccharides, peracetylated aryl glycosides for example, exhibit bands in the 800-1000 cm region and are characteristic for differentiating a- and p anomers. The relative intensities of C-O-C stretching vibrations in the 1000-1100 cm region and a band near 300 cm for -anomers are criteria for differentiating anomeric peracetylated alkyl and aryl glycosides [11]. 

An additional advantage of permethylation of oligosaccharides was demonstrated by Delaney and Vonros [41]. These componnds can be efficiently separated by reversed-phase LC (RPLC), including differentiation between a and 3 anomers. 

This, however, is interpreted by the authors as a consequence of differential solvatation (31). When the lithium salt of 2,3,4,6-tetra-0-benzyl-D-glucose is prepared in benzene and tetrahydrofuran, there are equal proportions of both anomers, but we do not know whether equilibrium has been reached in this experiment (32). 

Gabryelski, W. Froese, K.L., Rapid and sensitive differentiation of anomers, linkage, and position isomers of disaccharides using high-field asymmetric waveform ion mobility spectrometry FAIMS, J. Am. Soc. Mass Spectrom. 2003, 14, 265-277. 

Previous assignments of bands characteristic of furanose and pyranose forms (Mathlouthi, Carbohydr. Res., 1980, 7, 225) were shown to be incorrect since these bands co-occur in the spectra of crystalline -D-fructopyranose. Prom the intensity of the carbonyl absorption in fructose solutions (the 0 -deuterated form in D-O) relative to that of diethyl ketone, it was concluded that 0.9 of fructose was present as the open-chain form. From a study of the i.r. spectra of peracetylated aryl glycosides, the value of bands in the 800-1000 cm region for differentiating a- and 6-anoraers has been reassessed. The relative intensities of C-O-C stretching vibrations in the 1000-1100 cm region and a band near 300 cm for -anomers only were suggested as criteria for... 

Notes and discussion. This procedure is used for the stereoselective formation of a, 2-trans configured fluoride. The use of the orthoester precursor allows differentiation of the 0-2, which is a strategic manipulation that is often useful in oligosaccharide synthesis. The product also has participatory acetyl protection of 0-2, which may be used to direct the stereochemistry of its glycosylation reaction. The direct treatment with DAST has the advantage that only a single anomer is formed, compared to the anomeric mixture which results from the two step process of hydrolysis to the hemiacetal followed by DAST treatment. 

Magaud D, Dohnazon R, Anker D, Doutheau A, Dtuy YL, Deslongchamps P (2000) Differential reactivity of a- and P-anomers of gfycosyl accepters in glycosylations. A remote consequence of the endo-anomeric effect Org Lett 2 2275-2277... 

The chromatographic conditions used for the sugars (section IV, 1) are suitable for the methyl glycosides which migrate somewhat faster than the free sugars. It is apparent that the a and j8 anomers are readily differentiated and in the few glycosides examined the anomer has the higher hi / value [4, 16]. 

Aspects of chemical methods used in the structural elucidation of polysaccharides and complex carbohydrates have been reviewed. In a critical examination of the use of g.l.c.-m.s. in the identification of TMS ethers of monosaccharides, a standardized method, which uses a medium resolution mass spectrometer and short chromatographic columns, has been proposed. TMS Ethers of monosaccharides have been characterized by g.l.c.-chemical ionization m.s. with ammonia as reagent gas. Molecular weights were determined, and fragment ions were produced in a quantity high enough to differentiate between stereoisomers (epimers and anomers). Disaccharides have been determined by permethylation followed by g.l.c. The method has been used in the detection of carbohydrate intolerance secondary to intestinal disaccharidase deficiency. 

HPLC. Due to the lack of resolution in SEC, HPLC was used to improve resolution. Furthermore a detector based on optical rotation was adapted to the HPLC equipment and connected in series with the differential refractometer. It is known 9) that molar optical rotation includes contributions from the chemical structure of the molecules [m], its conformation [A] and the relative amounts of anomers according to the relation ... 

Thus, the susceptibility of the pigment to the action of /3-glucuroni-dase had already established the identity of one of the two sugar residues as the D-enantiomer of glucuronic acid. It further gave proof for its presence as the /8-anomer but did not differentiate between the alternative pyranoside and furanoside structures. This information cannot be deduced from enzymic studies since both forms are almost equally susceptible to the action of /8-glucuronidase (Kato et al, 1964a,b). 

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