Glucose esterification

Cellulose triacetate is obtained by the esterification of cellulose (qv) with acetic anhydride (see Cellulose esters). Commercial triacetate is not quite the precise chemical entity depicted as (1) because acetylation does not quite reach the maximum 3.0 acetyl groups per glucose unit. Secondary cellulose acetate is obtained by hydrolysis of the triacetate to an average degree of substitution (DS) of 2.4 acetyl groups per glucose unit. There is no satisfactory commercial means to acetylate direcdy to the 2.4 acetyl level and obtain a secondary acetate that has the desired solubiUty needed for fiber preparation. 

Insulin stimulates lipogenesis by several other mechanisms as well as by increasing acetyl-CoA carboxylase activity. It increases the transport of glucose into the cell (eg, in adipose tissue), increasing the availability of both pyruvate for fatty acid synthesis and glycerol 3-phosphate for esterification of the newly formed fatty acids, and also converts the inactive form of pyruvate dehydrogenase to the active form in adipose tissue but not in liver. Insulin also—by its ability to depress the level of intracellular cAMP—inhibits lipolysis in adipose tissue and thereby reduces the concentration of... 

Adipose tissue Storage and breakdown of triacylglyc-erol Esterification of fatty acids and lipolysis lipogenesis Glucose, lipoprotein triacylglycerol Free fatty acids, glycerol Lipoprotein lipase, hormone-sensitive lipase... 

Figure 12 Lipase-catalyzed regioselective esterification of glucose in a mixed...

S (2)-hydroxy-3-butenenitrile from acrolein and HCN trans hydrocyanation using, for instance, acetone cyanohydrin Hydrolysis of nitriles to amides, e.g. acrylonitrile to acrylamide Isomerization of glucose to fructose Esterifications and transesterifications Interesterify positions 1 and 3 of natural glycerides Oxidation of glucose to gluconic acid, glycolic acid to glyoxalic acid... 

Acetamiprid and its metabolites. A GC method has been developed for the determination of acetamiprid and its metabolites IM-2-1, IM-0, IC-0 (Figure 4) and IM-O-glucose in crops. As shown in Figure 5, acetamiprid and its metabolites in crops are extracted with methanol and derivatized to methyl 6-chloronicotinate (IC-O-Me) through alkaline hydrolysis, potassium permanganate oxidation and then esterification... 

Acylation of jS-D-glucose with azolides yields preferentially esterification in the 1-position of which for example, with R = C6H5 60% and with R=Ci7H35 71% yield are obtained. Azolides of sterically crowded acids [R = (C6H5)2CH or (CH3)3C] give poorer yields ( 28%).[193]... 

The reaction of crocetin bisazolide has also been achieved with unprotected ( ) / -D-glucose in excellent yields (67% from the imidazolide 70% from the 1,2,4-triazolide). Esterification takes place exclusively at the anomeric C-atom, and produces only the f -anomer. The higher acidity of the anomeric hydroxyl group compared with the other... 

The ratio of the a- to the j -anomeric D-glucosyl ester can be influenced by changing the reaction conditions. In DMF the a-anomer of the crocetin bis(D-glucosyl ester) was formed in about 70% yield.[196] Esterification of D-glucose with the imidazolides of benzoic acid or stearic acid in pyridine furnished a mixture of the a- and j -anomers of the C(l) glucosyl ester.[196]... 

The regioselective esterification at position 6 of a-D-glucose and a-D-glucopyrano-sides with fatty acids [81] is readily achieved by use of Novozym 435, in accordance with Scheme 8.56. 

Direct esterification of D-glucose by heating with 50% acetic acid at 100° was reported to yield 26-30% of the 6-acetate after chromatography on cellulose, together with unchanged starting-material and... 

Esterification of 2,4-D with plant constituents via conjugation formed the p-D-glucose ester of 2,4-D (Thomas et ah, 1964). 

Sugar The hydrolysis of sucrose in the intestine produces both glucose and fructose, which are transported across the epithelial cells by specific carrier proteins. The fructose is taken up solely by the liver. Fructose is metabolised in the liver to the triose phosphates, dihydroxy-acetone and glycer-aldehyde phosphates. These can be converted either to glucose or to acetyl-CoA for lipid synthesis. In addition, they can be converted to glycerol 3-phosphate which is required for, and stimulates, esterification of fatty acids. The resulting triacylglycerol is incorporated into the VLDL which is then secreted. In this way, fructose increases the blood level of VLDL (Chapter 11). 

Figure 16.1 The glucose/fatty add cycle. The dotted Lines represent regulation. Glucose in adipose tissue produces glycerol 3-phosphate which enhances esterification of fatty acids, so that less are available for release. The effect is, therefore, tantamount to inhibition of lipolysis. Fatty acid oxidation inhibits pyruvate dehydrogenase, phosphofructokinase and glucose transport in muscle (Chapters 6 and 7) (Randle et al. 1963).

Figure 16.3 Effects of insulin on the glucose/fatty acid cycle. Insulin enhances glucose metabolism by stimulating glucose uptake by muscle and adipose tissue and by inhibiting lipolysis in adipose tissue (see Chapter 12 for the mechanism of these effects). The effect of glucose metabolism on lipolysis is via stimulation of fatty acid esterification via glycerol 3-phosphate.

One of the consequences of forming a cyclic hemi-acetal or hemiketal is that the nucleophilic hydroxyl adds to the carbonyl group and forms a new hydroxyl. This new group is susceptible to many normal chemical reactions of hydroxyls, e.g. esterification, and this type of reaction effectively freezes the carbohydrate into one anomeric form, since the ringopening and equilibration can now no longer take place. Consider esterification of glucose with acetic anhydride (see Section 7.9.1). P-o-Glucose will be... 

Esterification. The hydroxyl groups of monosaccharides can form esters with acids. In metabolism, phosphoric acid esters such as glucose 6-phosphate and glucose 1-phosphate (6) are particularly important. 

It therefore appeared that a general mechanism for enzymatic esterification of phenolic acids with glucose was operative, whereas the reaction with other alcoholic moieties proceeded via carboxyl-activated acyl derivatives. [In this context it should be emphasized that glucose esters must not be confused with glucosides different enzymes are involved in the biosynthesis of these two types of phenolic glucose derivatives (36)]. 

Succinic acid. Succinic add is also available via fermentation of glucose, and has the potential to become a large-scale industrial chemical in the future. However, there are only a few reports on dehydration reactions involving succinic acids in the literature, and most of these are concerned with esterification to produce dialkyl esters. The synthesis of various dialkyl esters was reported using metal exchanged montmorillonite clays (Na, Mn ", ... 

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