Other Derivatizations

Previous discussions have been primarily about the synthesis of NAN (N-acetylneuraminic acid) or its precursors, and in some cases the N-glycolyl (N GN) derivative has been mentioned. Yet, as was shown in 

In 1969, Schoop et aL found that pig submaxillary slices could synthesize NGN from acetate, N-acetylmannosamine, or N-acetylneu-raminic acid, all labeled in the acetate moiety. Schauer (1970a 1970Z ) demonstrated an enzyme system in high-speed supernatants of hog submaxillary gland extracts capable of oxidizing N-acetylneuraminic acid or A -acetylmannosamine to A/ -glycolylneuraminic acid. The enzyme is called N-acetylneuraminaterOg-oxidoreductase and requires O2 and ascorbate or NADPH for activity. It appeared that free N-acetylneuraminic acid is the substrate, but it is possible that CMP-NAN or the 9-phosphate ester is the substrate. 

O-acetylation has also been demonstrated by Schauer (1970c,t/) using slices of horse and bovine submaxillary gland. Acetyl-CoA appears to be the donor, and again free NAN or its 9-phosphate ester or CMP-NAN appear to be the acceptors. In a later paper (Schauer and Wember, 1971), both hydroxylation and O-acetylation of membrane-bound polymer NAN was demonstrated. Until these enzyme systems are solubilized and purified, it is not clear at what level derivatization (hydroxylation and O-acetylation) occurs. Schauer (1972) has presented a model which involves specific enzymes which catalyze transfer of CMP-NAN to polymers. All of the enzymes are arranged in a multienzyme membrane-bound complex. This interesting model awaits experimental verification. 

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Diesters. Many of the diester derivatives are commercially important. The diesters are important plasticizers, polymer intermediates, and synthetic lubricants. The diesters of azelaic and sebacic acids are useflil as monomeric plasticizing agents these perform weU at low temperatures and are less water-soluble and less volatile than are diesters of adipic acid. Azelate diesters, eg, di- -hexyl, di(2-ethylhexyl), and dibutyl, are useflil plasticizing agents for poly(vinyl chloride), synthetic mbbers, nitroceUulose, and other derivatized ceUuloses (104). The di-hexyl azelates and dibutyl sebacate are sanctioned by the U.S. Food and Dmg Administration for use in poly(vinyl chloride) films and in other plastics with direct contact to food. The di(2-ethylhexyl) and dibenzyl sebacates are also valuable plasticizers. Monomeric plasticizers have also been prepared from other diacids, notably dodecanedioic, brassyflc, and 8-eth5lhexadecanedioic (88), but these have not enjoyed the commercialization of the sebacic and azelaic diesters. 

Other derivatizing reagents that can be used as simple and efficient reagents for determining the enantiomer composition of chiral alcohols using the 31P NMR method are shown below (Scheme 1-9 and Fig. 1-11)29 32 ... 

The most important advantage of OPA over other derivatization reagents is that it quickly reacts with amines and enables the BAs to be detected at femtomole levels. The drawback is that OPA reacts only with primary amines and leads to poorly stable compounds (120). Better results are obtained with DNS that also reacts with secondary amines and gives stable compounds that can be treated in subsequent concentration steps without using an automated system (103,121,5). 

We have also employed other derivatization techniques to selectively label other moieties such as carbonyls and applied these to the selective detection of steroids [119]. Girard s Reagent P reacts with the carbonyl-containing compounds according to Equation 5. 

Other derivatization procedures involve alkylation and silylation [486]. The latter is carried out with the aid of BSTFA and provides simple products, whereas alkylation with a methyl iodide—sodium hydride—dimethyl sulphoxide mixture (50°C, 10 min) leads to two peaks due to various products. 

Silylation reagents Esterification reagents Other derivatizing reagents Various reaction (micro)vials and other accessories... 

Perfluoro)acyl anhydrides Common silylation reagents Other derivatizing agents Reaction tubes for GC-derivatization... 

Ogawa and Fritz (1985) developed a method for the identification of acrolein in water. A known volume of water is passed over a column of zeolite that traps the acrolein. The column is then eluted with acetonitrile, and derivatization using DNP follows. By following this procedure, a sample that can be analyzed by HPLC is obtained. Other derivatizing agents that have been used successfully for the monitoring of acrolein in the environment include dimedon, phenylhydrazone, 4-hexylresorcinol, and 3-methyl-2-benzothiazolone (Altshuller and McPherson 1963 Peltonen et al. 1984). 

Higher alkenes can be obtained from thermal cracking of wax, and although a thermodynamic mixture of internal alkenes might have been expected, the wax-cracker product contains a high proportion of 1-alkenes, the kinetically controlled product. For the cobalt-catalyzed hydroformylation the nature of the alkene mixture is not relevant, but for other derivatizations the isomer composition is... 

Various other derivatization strategies have been reported, e.g., V-(2-diethylamino)ethyl-4-aminobenzamide [7], 2-aminonaphthalene trisulfone (ANTS) [60], 2-amino-5-bromopyridine [61]. With the latter label, isotope tagging of the oligosaccharides is achieved, enabhng easy access to sequence information through the diagnostic twin peaks. 

In later studies, other derivatization agents were proposed to enhance the... 

Apart from ninhydrin, many other derivatization reagents have been used both precolumn and postcolumn derivatization modes have been extensively employed [3-5]. Derivatization procedures offer significant advantages in both separation and detection aspects and, thus. 

The main reasons for derivatization of steroids are to decrease heat sensitivity of steroids to avoid irreversible adsorption of steroids onto the stationary phase to increase volatihty of steroids to increase the separation efficiency to achieve enhanced selectivity of the separations, and to improve the sensitivity of the detectors. Segura et al. described some important general requirements for derivatization reactions, i.e., a single derivative should be formed for each analyte the reaction should be simple and rapid, and they should occur under mild conditions the derivate should be stable, reproducible, and produced with high yield in quantitative analyses, the calibration curve should be linear. The main derivatization method for steroids is silylation, but other derivatization methods using, for example, acetic acid anhydride, trifluoroacetic anhydride (TFA), pentafluoro-propionic acid (PFPA), or heptafluoroabutyric anhydride (HFBA) could also be used. " For anabolic steroids... 

Because a number of powerful synthetic and natural nonsaccharide sweeteners are available on the market, apart from reduction to saccharide alcohols, other derivatizations of saccharides, even if they increase their sweetness (Table 5.3), have no practical significance. 

Other derivatization possibilities of thiols include silylation (Figure 10.4) with N-(tert-butyldimethylsilyl)-Af-methyltrifiuoroacetamide (MSTFA) and acylation using Af-methylbis (trifiuoroacetamide) (MBTFA). 

Derivatized with BSTFA others derivatized with MSTFA-TMSl-DTE (1000 2 2, v/v/w). 

In another publication (10), we indicated that compound 2 can undergo hydrolysis and possibly other derivatization reactions. In this paper, we have followed up on that work and carried out several reactions, particularly with enzymes, in order to fully explore the chemistry and the utility of these new biobased materials. 

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