Long-chain carbohydrates, synthesis

U. Aich and D. Loganathan, Zeolite-catalyzed Helferich-type glycosylation of long-chain alcohols. Synthesis of acetylated alkyl 1, 2-trans glycopyranosides and alkyl 1, 2-cis C2-hydroxy-glycopyranosides, Carbohydr. Res., 342 (2007) 704-709. 

Use of Unstabilized Carbohydrate Ylides for the Synthesis of Long-Chain Carbohydrates... 

To summarize, unstabilized carbohydrate phosphoranes are useful entities for the synthesis of long-chain carbohydrates by a Wittig process as long as the proper experimental conditions are employed and as long as the 6-oxygen is attached by another set of bonds to... 

The methods often used for the branching of carbon chain are also suitable for the chain extension of sugars at both ends (e.g., C-l and C-5/C-6). Several developments of chain extension have recently culminated in the synthesis of long-chain carbohydrates of biological interest. 

A review on the synthesis and reactivity of sugars with two branches at C-3 has appeared, as well as another on the synthesis of rare carbohydrates which includes the application of "naked sugars" to the synthesis of branched, long chain carbohydrates amongst the topics covered. ... 

The source of long-chain fatty acids is either dietary lipid or de novo synthesis from acetyi-CoA derived from carbohydrate. Fatty acids may be oxidized to acetyl-CoA (P-oxidation) or esterifred with glycerol, forming triacylglycerol (fat) as the body s main fuel reserve. 

Hepatic steatosis usually is a result of excessive administration of carbohydrates and/or lipids, but deficiencies of carnitine, choline, and essential fatty acids also may contribute. Hepatic steatosis can be minimized or reversed by avoiding overfeeding, especially from dextrose and lipids.35,38 Carnitine is an important amine that transports long-chain triglycerides into the mitochondria for oxidation, but carnitine deficiency in adults is extremely rare and is mostly a problem in premature infants and patients receiving chronic dialysis. Choline is an essential amine required for synthesis of cell membrane components such as phospholipids. Although a true choline deficiency is rare, preliminary studies of choline supplementation to adult patients PN caused reversal of steatosis. 

The synthesis of long-chain fatty acid esters of carbohydrates is inherently more demanding. It was found that glucose did not react with vinyl laurate in a pure ionic liquid medium, but in biphasic tert-butyl alcohol/[BMIm][PF6], glucose could be acylated by the vinyl esters of O, 2-Cu, fatty acids. The best results were obtained with CaLB, which was twice as active as TIL, and the selectivity for acylation at C-6 was high [114]. The esterification of glucose with palmitic acid, which is, in an industrial context, to be preferred over transesterification, has recently been demonstrated in tert-butyl alcohol/[BMIm][PF6] medium [115]. 

In addition to long-chain fatty acids from plasma, the major nutrients utilized for milk fat synthesis are glucose, acetate and 0-hydroxybutyrate. Kinetics for the uptake of these from blood were reported by Miller et al. (1991). Glucose is absolutely required for milk synthesis, being a precursor for lactose or other carbohydrates, or both, in all terrestrial mammals (Oftedal and Iverson, 1995). 

Gilchrist accepted the position, working on the separation of long-chain hydrocarbons with the Austrian scientist Berta Karlik,28 and then on the synthesis of fats containing a carbohydrate unit. 

A new procedure for GSL synthesis via olefin cross metathesis (164) is highly versatile in terms of the hydrophobic agly-cone. A protected 5 carbon amino alkene diol is the central building block to which the protected carbohydrate donor, long chain fatty acid, or, by olefin cross metathesis, the long alkenyl chain of the base can be coupled, in a variety of sequences. This atypical synthetic flexibility should allow a stmctural approach to dissecting the role of the lipid moiety in GSL receptor function and intracellular trafficking. 

The KQ is influenced by the net rate of fatty acid biosynthesis. Fatty acid synthesis involves the conversion of carbohydrate, via the acetyJ-CoA intermediate, to long-chain fatty acids. The synthesis of fatty acids requires reduced NADP as a co/ac-tor. It involves the consumption of two molecules of NADPH + H+ for each 2-carbon unit incorporated into the fatty acid. The NADPH + H is supplied by two separate pathways the pentose phosphate pathway (PPP) and the malic enzyme/citrate Lyase pathway. 

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