Carbohydrates cleavage

A liquid membrane bioreactor was developed as a means of encapsulation for a multi-enzyme system incorporating an oxidation and carbohydrate cleavage, demonstrated using a-glucosidase and glucose oxidase in the conversion of maltose to gluconic acid ... 

H. Weenen and W. Apeldoorn, Carbohydrate cleavage in the Maillard reaction. In Flavour Science Recent Developments, Vol. 197, A. J. Taylor and D. S. Mottram (eds), Royal Society of Chemistry, Cambridge, 1996, 211-216. 

For clinical application as a protein-deglycating enzyme, however, the carbohydrate cleavage in A/ -D-fructose-L-lysine on glycated proteins is needed, and a search for enzymes eapable of such activity has been ongoing for the past two decades (Table V). Most of the characterized fungal fructose-amino acid oxidases carry a relatively high... 

Cooperativity/competUion among acceptors (armed/disarmed carbohydrates) Cleavage of the C-X bond at the anomeric position proceeds via evolution of the anomeric n o C-X interaction that culminates in the oxocarbenium ion. This carbocation is so strongly stabilized by n j- p interaction that this interaction is commonly described as a dative it-bond. Because oxacarbenium ions are strongly stabilized, their formation is relatively facile. In cross-coupling glycosylalion reactions, however, it is beneficial to differentiate the reactivity of two saccharides for the selectivity reasons. The competition and cooperativity between stereoelectronic effects can be used to fine-tune the reactivity of anomeric systems. 

Periodic acid cleavage of vicinal diols is often used for analytical purposes as an aid m structure determination By identifying the carbonyl compounds produced the con stitution of the starting diol may be deduced This technique finds its widest application with carbohydrates and will be discussed more fully in Chapter 25... 

Cleavage reactions of carbohydrates also occur on treatment with aqueous base for prolonged periods as a consequence of base catalyzed retro aldol reactions As pointed out m Section 18 9 aldol addition is a reversible process and (3 hydroxy carbonyl com pounds can be cleaved to an enolate and either an aldehyde or a ketone... 

Heterogeneous reaction (Section 6 1) A reaction involving two or more substances present in different phases Hydro genation of alkenes is a heterogeneous reaction that takes place on the surface of an insoluble metal catalyst Heterolytic cleavage (Section 4 16) Dissociation of a two electron covalent bond in such a way that both electrons are retained by one of the initially bonded atoms Hexose (Section 25 4) A carbohydrate with six carbon atoms High density lipoprotein (HDL) (Section 26 11) A protein that carries cholesterol from the tissues to the liver where it is metabolized HDL is often called good cholesterol Histones (Section 28 9) Proteins that are associated with DNA in nucleosomes... 

The anomeric position of a carbohydrate was protected as its trichloroethyl ether. Cleavage is effected with Zn, AcOH, AcONa (3 h, 92%). ... 

Benzylidene acetals have the useful property that one of the two C-O bonds can be selectively cleaved. The direction of cleavage is dependent upon steric and electronic factors, as well as on the nature of the cleavage reagent. This transformation has been reviewed in the context of carbohydrates.""... 

The removal of the carbohydrate auxiliary group and the hydrolysis of the amino nitriles is achieved by acidolytic cleavage of the hemiaminal /V-glycosidic bond and the concomitant acid-catalyzed solvolysis of the nitrile using either hydrogen chloride in formic acid or hydrogen bromide in acetic acid56 57. 

Kaneko C., Katagiri N., Nomura M., Sato H. A New Method for the Stereoselective Synthesis of Nucleosides by Means of Sodium Borohydride Mediated Reductive C-C or C-N Bond Cleavage Reaction Isr. J. Chem. 1991 31 247-259 Keywords carbohydrates... 

Because of its importance to carbohydrate technology, biochemistry, and physical organic chemistry, the hydrolytic cleavage of glycosides has been extensively studied with respect to both acid and enzymic catalysis. Reviews on the acid-catalyzed hydrolysis have been presented by BeMiller, Capon, ... 

Arya DP (2006) Diazo and Diazonium DNA Cleavage Agents Studies on Model Systems and Natural Product Mechanisms of Action. 2 129-152 El Ashry ESH, El KUany Y, Nahas NM (2007) Manipulation of Carbohydrate Carbon Atoms for the Synthesis of Heterocycles. 7 1-30 El Ashry ESH, see El Nemr A (2007) 7 249-285... 

The oxidative cleavage of v/c-diols to give two carbonyl functions (Eq. 5.3) by periodates was first observed by Malaprade and has since been widely applied to the carbohydrate area.50 Since both the reagent sodium periodate and the carbohydrate substrate are water soluble, the reaction is usually carried out in aqueous media.51 The reaction has been applied to polysaccharides such as starch.52 The periodate oxidations of sodium alginate in water as well as a dispersion in 1 1 ethanol-water mixture have been compared.53 Because sodium alginate forms a highly viscous solution, the oxidation was observed to be more extensive in ethanol-water. 

Photolabile linkers play an important role in solid-phase organic synthesis (SPOS) due to their stability under both acidic and basic conditions. The ONb photolabile linker was modified to improve cleavage rates and yields Fmoc-Tos-OFI was released in 87% yield after 23 h (Scheme 4) [24]. Specifically, the primary alcohol was changed to a secondary benzylic alcohol and the attachment to the resin was through an alkyl chain as opposed to an amide function. Linker 20 was used for the production of carboxylic acids or carbohydrates. A second example... 

---