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The review considers the known strategies for the synthesis of fragments of arabinogalactan and lipoarabinomannan, polysaccharides that are contained in the cell walls of causative agent of tuberculosis Mycobacterium tuberculosis, as well as other related oligosaccharides containing arabinofuranose residues, using silyl substituents both for the differentiation of hydroxy groups in monosaccharide blocks and as stereodirecting groups during formation of a β-arabinofuranoside bond. In particular, the use of silyl groups (in combination with orthogonal to them acyl groups) allows the stereoselective synthesis of arabinans without the involvement of benzyl groups removable under reducing conditions, which is unacceptable in the presence of fragments sensitive to hydrogenolysis. This significantly simplifies the synthesis of 1,2-cis-linked oligosaccharides containing multiple bonds or azide groups, in particular, in aglycone, which is extremely important for the preparation of neoglycoconjugates both by converting the azide to an amine, followed by covalent binding to a carrier, and by conducting click-chemistry reactions using the 1,3-dipolar cycloaddition of azides to alkynes. [ABSTRACT FROM AUTHOR]

A series of new trichloromethyl- and alkoxy-substituted pyrido[2,3-d]pyrimidine derivatives were obtained from trichloromethyl-substituted pyrimidines with vicinal amino and acyl groups synthesized based on the reaction of trichloroacetonitrile with β-diketone diaminomethylidene derivatives. [ABSTRACT FROM AUTHOR]

Stereoselective synthesis of α-sialosides by the glycosylation reaction (sialylation) is an important task in carbohydrate chemistry. Using quantum chemical calculations, the conformations of the sialyl cation formed from the sialyl donor under conditions of sialylation reaction were studied. Although the "axial conformation" of sialyl cation itself is energetically unfavorable, it is possible to stabilize it through the participation of O- and N-acyl protective groups. The obtained results open the possibility to modulate the stereoselectivity of sialylation by directed variation of the nature of protective groups in the sialyl donor molecule. 2 [ABSTRACT FROM AUTHOR]