Chitobiose synthesis

The combination of the N-terminal allyloxycarbonyl (Aloe) group (34) with the tert-butyl ester proved to be a particularly efficient tool in the synthesis of complex glycopeptides, as has been demonstrated in the synthesis of sensitive fucosyl chitobiose glycopeptides (19). The Aloe group was... 

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]. 

H. Kunz and C. Unverzagt, Protecting group-dependent stability of intersaccharide bonds— synthesis of a fucosyl-chitobiose glycopeptide, Angew. Chem. lnt. Ed. Engl. 27 1697 (1988). 

Fig. 12. Synthesis of glycosyl amine by amination of reducing sugar (chitobiose) (97).

Kunz, H. and Unverzagt, C. (1988) Protecting-group-dependant stability of intersaccharide bonds-Synthesis of a fucosyl-chitobiose glycopeptide. Angew. Chem. Int. Ed. 27, 1697-1699. 

SCHEME 11.21 Synthesis of EPO bearing three N-linked chitobioses and an O-linked tetrasaccharide. 

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. 

W. GUnther and H. Kunz, Synthesis of a P-mannosyl-chitobiose-asparagine conjugate—a central core region unit of the A-glycoproteins, Angew. Chem. Int. Ed. Engl. 29 1050 (1990). 

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. 

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