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Sugars elimination reactions

Note that the key to Maxam-Gilbert sequencing is to modify a base chemically so that it is removed from its sugar. Then piperidine excises the sugar from its 5 - and 3 -links in a /3-elimination reaction. The conditions of chemical cleavage described in Figures 12.4 and 12.5 are generally adjusted so that,... [Pg.361]

Cyclization of 148 with l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and a subsequent elimination reaction with acetic anhydride and pyridine furnished compound 149. °- Compound 149 was found to be an important key compound for the following synthesis of carba-sugars of the a-L-altro, fi-D-gluco, P-h-allo, and a-D manno modifications. [Pg.45]

As acylation of aldonolactones is related to -elimination reactions, the fully acylated aldonolactone derivatives are mentioned in Section IX (see also Sections VI and VIII). Only a few studies on selective acylation of aldonolactones have been described. The partially acylated derivatives have been employed as glycosylating agents or for the preparation of monometh-ylated sugars. [Pg.132]

DNA-(apurinic or apyrimidinic site) lyase [EC 4.2.99.18, formerly EC 3.1.25.2] acts on the C-Q-P bond 3 to the apurinic or apyrimidinic site in DNA. This bond is broken by a /3-elimination reaction, leaving a 3 -terminal unsaturated sugar and a product with a terminal 5 -phosphate. Note that this nicking of the phosphodiester bond is a lyase-type reaction, not hydrolysis. [Pg.191]

FIGURE 9 Isomerization and elimination reactions (a) The conversion of glucose 6-phosphate to fructose 6-phosphate, a reaction of sugar metabolism catalyzed by phosphohexose isomerase. (b) This reaction proceeds through an enediol intermediate. The curved blue ar-... [Pg.487]

Conversion of sugar phenylhydrazones into olefinic azo-sugars on treatment with acetic anhydride and pyridine was shown by Wolfrom and co-workers (28) (The acetylated forms of the acyclic phenylhydrazones of D-glucose, D-mannose, and D-galactose readily lose the elements of acetic acid to yield 1-phenylazo-frans-l-hexenetetrol tetraacetate when treated with warm aqueous ethanol (28, 30). It is assumed that atmospheric oxygen partakes in this elimination reaction.) This is a special case of base catalyzed -elimination reactions of the type proposed by Isbell in 1943 ( 31), involving consecutive electron displacement (which actu-... [Pg.103]

The presence of such enolic ions in alkaline solutions of sugars was shown later by Isbell et al. (67). The mechanism of the alkaline -elimination reaction of substituted serine and threonine glycosidases based on this concept is shown in Figure 9. [Pg.241]

The H02 elimination reactions of the peroxyl radicals derived from polyhydric alcohols and from neutral sugars,0, 8 u8 are discussed in more detail later (see Sects. Ill,lb and 2b, respectively). [Pg.24]

Some of the sugars that are formed in the radiolysis of Thd also have the C(4 ) radical as precursor (Dizdaroglu et al. 1976) (for a quantum-chemical study of conformation of the C(4 ) radical and hyperfine coupling constents see Parr and Wetmore 2004). The water elimination reactions as depicted in reactions (285) and (288) are generally proton-catalyzed. Yet, the ensuing products are also observed in neutral solution. Their yields are given in Table 10.27. [Pg.296]

The elimination of benzoylated 1,4-aldonolactones in pyridine is difficult to control, and further elimination reactions take place, decreasing the yield of monounsaturated derivative and consequently of the 3-deoxy sugar.83... [Pg.157]

Phenylselenoetherification (8,26-28). A related reaction leading to a potential precursor to deoxy sugars has been reported by Current and Sharpless. Thus the reaction of p-chlorobenzeneselenenyl bromide (6, 421) with (E)-4-hexenal (1) in CCI4 containing benzyl alcohol at reflux leads to 2 in about 65% yield. This product is converted into 3 on selenoxide elimination. When benzeneselenenyl bromide itself is used, this elimination reaction is very slow. The unsaturated compound can be functionalized in various wa3 . Of course, alcohols other than benzyl alcohol can be used. [Pg.18]

Here we discuss new types d cellulose derivatives synthesized by nucleophilic substitution of mixed polysaccharides containing repeating units of 2,3- and 3,6-anhydro sugars, units d amino sugars, their N-alkyl(aryl)- and N-carboxylalkyl(aryl) derivatives, alkyl derivatives and phenylbarenyl derivatives d deoxygliux)se, elimination reactions of unsaturated derivatives containing multiple C-C bonds in the... [Pg.88]


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See also in sourсe #XX -- [ Pg.28 , Pg.290 ]




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