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A separation-friendly Mitsunobu reaction using hydrophobic-tagged acids is reported. Commercially available or simply prepared and recyclable hydrophobic-tagged acids can react with various alcohols to afford the target products in high yield with easy purification based on C-18 silica solid-phase extraction or normal silica gel filtration.

Based on a pre-activation protocol, the stereoselectivity of oxazolidinone-protected amino sugar thioglycoside donors towards glycosylations can be controlled by additives. Either α- or β-selectivity could be obtained by changing additives. 2,4,6-Tri-tert-butylpyrimidine (TTBP) was the best β-directing additive, while thiophene worked as the best α-directing additive. The bifunctional additives such as tetrabutyl ammonium iodide (TBAI) afforded either α- or β-selectivity depending on the amount added. Poor α-­selectivity of some glycosylations without any additives was greatly improved by adding TBAI or thiophene.

An efficient preactivation protocol for the highly α-stereo-selective glycosylation of2-deoxy- and 2,6-dideoxysugars has been developed using acetyl-protected 2-deoxy- and 2,6-dideoxythioglycosides as glycosyl donors. The approach allows a wide range of glycosyl acceptors and donors to be used.

Benzenesulfinyl morpholine (BSM) has been applied as a new promoter for the activation of thioglycosides. This proceeds by the in situ reaction of BSM with trifluoromethanesulfonic anhydride, which subsequently activates thioglycosides for glycosylations. Importantly, this reagent works well in our pre-activation one-pot oligosaccharide assembly strategy.

The regioselective reduction of one azido group in glycopyranoside and mannitol derivatives containing two azido functions with triphenylphosphine is described. In cyclic substrates with two secondary azides, equatorial azides were reduced in good yields in preference to axial azides. Steric, but not electronic, factors appear to determine the regiochemical outcome of the Staudinger reduction.