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Abstract: Two α-d-arabinofuranosyl oligosaccharides (2 and 3) found as constituent parts of the polysaccharide portion from the cell wall of Mycobacterium tuberculosis have been efficiently synthesized via a one-pot glycosylation procedure in which a key step is the chemoselective activation between d-arabinofuranosyl trichloroacetimidate donor 4 and partially protected aryl thioglycosides 5 or 7, respectively. [Copyright &y& Elsevier]

In this study, we designed a method to prepare 2-deoxy-2-azido-α- d -galactopyranosidic bonds using 4,6-di-O-benzylidenyl-3-O-t-butyldiphenylsilyl protected 2-deoxy-2-azido-1-thio- d -galactopyranoside 5 as donors. The donor 5 gives a good to excellent α-selectivity in the glycosylation with secondary alcohols, which was found to be associated with the benzylidenyl on 4,6-di-O and TBDPS on 3-O of the donor 5. Compared with results of the donor 6 and 7 , the 3-O-TBDPS could increase the activity of the thioglycoside, and the lone pairs on 4,6-di-O-benzylidenyl group enhanced the gg-cofnormation, which plays a role in improving the stereoselectivity. Finally, this method was demonstrated through the synthesis of a α-galactosamine -containing pentasaccharide 26. Image 1 • Stereocontrolled synthesis of 2-deoxy-2-azido-a-D-Gal p. • Silyl ether improve the donor reactivity. • Synthesis of a pentasaccharide. [ABSTRACT FROM AUTHOR]

This paper describes a mild and efficient catalytic deprotection method for isopropylidene ketals and benzylidene acetals using AcOH/H 2 O/DME(1,2-Dimethoxyethane). The method effectively removes ketal and acetal protecting groups from 2-deoxyglycosides which are prone to hydrolysis under acidic conditions. Moreover, it enables the selective removal of the terminal ketal over an internal one. [Display omitted] • A straightforward and efficient method for removing isopropylidene ketals and benzylidene acetals from 2-deoxyglycosides. • Selective deprotection of acetals and ketals in the presence of acid labile protecting groups. • Selective removal of the terminal ketal over an internal ketal. [ABSTRACT FROM AUTHOR]

We describe a β-L-arabinofuranosylation method by employing the 5- O -(2-pyridinecarbonyl)-L-arabinofuranosyl trichloroacetimidate 10 as a donor. This approach allows a wide range of acceptor substrates, especially amino acid acceptors, to be used. Stereoselective synthesis of β -(1,4)-L-arabinofuranosyl-(2S, 4R)-4-hydroxy-L-proline ( β -L-Ara f -L-Hyp 4 ) and its dimer is achieved readily by this method. Both the stereoselectivities and yields of the reactions are excellent. To demonstrate the utility of this methodology, the preparation of a trisaccharide in a one-pot manner was carried out. [ABSTRACT FROM AUTHOR]