Carbohydrates derivatization

D. J. Harvey, T. S. Mattu, M. R. Wormald, L. Royle, R. A. Dwek, and P. M. Rudd, Internal residue loss Rearrangements occurring during the fragmentation of carbohydrates derivatized at the reducing terminus, Anal. Chem., 74 (2002) 734-740. 

Harvey, D.J. (2000) Electrospray Mass Spectrometry and Fragmentation of n-linked Carbohydrates Derivatized at the Reducing Terminus. J. Am. Soc. Mass Spectrom. 11 900-915. 

Harvey DJ. Electrospray mass spectrometry and fragmentation of n-linked carbohydrates derivatized at the reducing terminus. J Am Soe Mass Speetrom. 2000 11 900-95. 

As mentioned previously, cellulosic phases as well as amylosic phases have also been used extensively for enantiomeric separations more recently (89,90). Most of the work ia this area has been with various derivatives of the native carbohydrate. The enantioresolving abiUties of the derivatized cellulosic and amylosic phases are reported to be very dependent on the types of substituents on the aromatic moieties that are appended onto the native carbohydrate (91). Table 3 fists some of the cellulosic and amylosic derivatives that have been used. These columns are available through Chiral Technologies, Inc. and J. T. Baker, Inc. 

Commercial derivatization of cellulose begins with the addition of sodium hydroxide to form alkaH cellulose (AC) (eq. 1, R = carbohydrate). 

Fortunately, derivatization for f.a.b.-m.s. makes no special demands on the carbohydrate chemist. The best derivatives are those that have been used for a very long time in carbohydrate work, namely, the per-O-acetyl and the per-O-methyl. Thus, f.a.b.-m.s. can be readily accommodated into existing structural programs. 

There are three main reasons for this choice. Firstly, it becomes more and more difficult to obtain recordable, molecular-ion signals from un-derivatized carbohydrates as their M, increases significantly above 3000. Secondly, the mass spectrometers that have been used in all high-mass-carbofiydrate studies published at the time of writing this article are not capable of very sensitive analysis above —3800 mass units (see later). Thirdly, at masses >4000, it is usually not practicable to work at the resolution necessary for adjacent peaks to appear as separate signals in the spectrum. To do so would require that the source and collector slits be narrowed to such a degree that there would be an unacceptable loss in sensitivity. Thus, spectra acquired at mass >4000 are usually composed of unresolved clusters. 

IonPac KC-811 column separated the labile compounds N-acetylneuraminic acid and N-glycolylneuraminic acid released by mild acid hydrolysis of bovine vitronectin.245 Sialic acid is extremely labile to conditions of handling and must be released by mild acid hydrolysis.246 Derivatization with phe-nylisothiocyanate and separation by reversed phase chromatography was found useful in analysis of hexosamines from gastric mucosa.247 A review on separation of sugars and other carbohydrates which covers many important aspects is available.248... 

Femia, R. E. and Weinberger, R., Determination of reducing and non-reducing carbohydrates in food products by liquid chromatography with post-column catalytic hydrolysis and derivatization comparison with refractive index detection, /. Chromatogr., 402, 127, 1987. 

In 1991, Whitesides etal. reported the first application of aqueous medium Barbier-Grignard reaction to carbohydrate synthesis through the use of tin in an aqueous/organic solvent mixture (Eq. 8.48).106 These adducts were converted to higher carbon aldoses by ozonolysis of the deprotected polyols followed by suitable derivatization. The reaction showed a higher diastereoselectivity when there was a hydroxyl group present at C-2. However, no reaction was observed under the reaction conditions when there was an /V-acctyl group present at the C-2 position. 

Gilbart, J. Fox, A. Morgan, S. L. Carbohydrate profiling of bacteria by gas chromatography-mass spectrometry Chemical derivatization and analytical pyrolysis. Eur. I. Clin. Microbiol. 1987, 6,715-723. 

In this chapter, we demonstrate the potential of such agents as catalysts/promoters in key steps for the derivatization of sugars. The most significant catalytic approaches in carbohydrate chemistry that use aluminosilicate porous materials, namely zeolites and montmorillonite clays, are reviewed and discussed. Silica gel is a porous solid silicate that has also been used for heterogeneous catalysis of organic reactions in general. We include here its usefulness as promoter and reagent support for the reactions under consideration. 

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

Oxidation is a widely used procedure in carbohydrate chemistry, mainly to access sugars that contain a carbonyl function to serve as valuable intermediates for a variety of derivatizations. Many procedures have been developed, employing either chemical or biochemical methodologies.14 148 While most of these methodologies rely on homogeneous catalysis, the use of heterogeneous catalysts has proved to be a feasible alternative.123c However, the utilization of catalysts based on silicon porous materials for the oxidation of carbohydrates is still a field to be further explored. 

---