Chitobiose derivative

In order to construct the L-asparagine derivative of per-O-acetylated 0-(2-acetamido-2-deoxy-/ -D-glucopyranosyl( 1 — 4)-2-acetamido-2-deoxy-D-glucose (7), Spinola and Jeanloz (13) used (the sensitive) silver azide for conversion of the a-chloro anomer of the chitobiose derivative 8 into the / -azido derivative 9. Kunz and associates (14,15) have accomplished the conversion of the a-chloro anomer of 8 into 9 using sodium azide in the presence of tri-n-octyl-methylammonium chloride as a phase-transfer catalyst in chloroform water. 

The last method is by intramolecular delivery (Scheme 43, d) 422-425 although elegant, this method has not yet found practical application in the synthesis of complex oligosaccharides. It remains to be seen if the method will work with the rather unreactive 4 -hydroxy group of chitobiose derivatives. This reactivity has been increased both by application of phthaloyl protection of the 2-amino groups and by application of the inverted conformation of l,6-anhydro-2-azido-2-deoxyglucopyranose. 8 ... 

Finally, Kren and coworkers have proposed the use of selectively acylated glycosides to be used as acceptors in a bi-enzymatic approach to the synthesis of di- and trisaccharides exploiting lipases/proteases and glycosidases (for instance, 6-0-acetyl-N-acetyl-D-glucosamine, 14, to give the corresponding chitobiose derivative 15) [44]. 

Chitin deacetylase has been used in the synthesis of partially and fully N-deacetylated 4-methyl umberlliferyl chitobiose derivatives as fluorogenic substrates for chitinase. Conversely, the reverse acylating action of chitin deacetylase has been used to prepare a partially N-acetylated chitosamine tetramer. The preparation of a 4-0-acetyl sialic acid derivative by a lipase OF-catalysed deacetylation of the peracetylated precursor has been reported. ... 

This strategy (Scheme 10) is rather close to that described by K. C. Nicolaou. The central block 37 has been prepared from a chitobiose derivative [17]. The option of the N-phthalimido participating group has also been selected (see Box 1). The in-... 

Fig. 15.1. The A/-glycan biosynthetic pathway, illustrating how the three classes of A/-glycans (high mannose, hybrid and complex glycans) are derived from a common biosynthetic precursor. The trimannosyl-chitobiose core, which is common to all A/-glycans, is outlined on the precursor A/-glycan. Glc, o Man, GIcNAc.

Similarly Thiem and Wiemann (92) conducted the galactosylation of the 2-acetamido-2-deoxy-D-glucose-L-asparagine derivative 183 and the chitobiose-L-asparagine derivative 187 to furnish the di- and trisaccharide derivatives 185 and 188, respectively, by using galactosyltransferase. 

Hydrolyzes chitobiose and higher analogs and protein derivatives by removing Af-acetyl-n-glucosamine from the non reducing end A /S-D-glucuronide + HzO — alcohol + D-glucuronic acid... 

Chitin was prepared by the catalysis of chitinase. Incubation of a chitobiose oxazoline monomer with chitinase form bacillus sp. in phosphate buffer afforded chitin in quantitative yield (122). Using regiospecific 3-0- and/ or 3 -0-methylated derivatives of a chitobiose oxazoline as new substrate monomers, 3-0-methylated chitin oligomers were produced by enzymatic oligomerization using chitinase (123). 

Sakamoto J, Kobayashi S. Enzymatic synthesis of 3-0-Methylated chitin oligomers from new derivatives of a chitobiose oxazoline. Chem. Lett. 2004 33 698-699. 

SCHEME 15.19 Synthesis of glycosyl amine 167 by amination of chitobiose and subsequent transformation into chitobiosyl-aspargine derivative 168. 

The glycosynthase methodology has been successfully extended to the enzymatic synthesis of /3-mannoside. The Glc519Ser mutant of the retaining /3-mannosidase (Man2a) proved to afford a catalytic conversion of the various acceptors with the a-mannosyl fluoride 97 as a readily accessible donor [159] (O Scheme 49). The chitobiose and GlcNAc derivatives, however, would not function as the acceptor. 

Chitin is the most abundant biomacromolecule in the animal field, which is found normally in invertebrates as a structural component. This important polysaccharide was synthesized for the first time by the enzymatic polymerization using chitinase and a chitobiose oxazoline derivative (Scheme 14).131 The latter activated monomer has a distorted structure with an a configuration at Cl, which resembles a transition-state structure of substrate chitin at the active site during a hydrolysis process (Scheme 15).3b 131132 The ring-opening polyaddition of the chitobiose oxazoline derivative was exclusively promoted by chitinase at pH 10.6, where the hydrolytic activity of chitinase was very much lowered. 

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