A mild, efficient, and selective procedure for transprotection of acetonides to acetates catalyzed with HClO4–SiO2

A mild acetolysis procedure for the regioselective removal of isopropylidene in di-O-isopropylidene-protected pyranoside systems

A mild acetolysis method for the regioselective removal of isopropylidene group from di-O-isopropylidene-protected hexopyranosides is reported. O-Isopropylidene-protected intermediates play an important role in carbohydrate chemistry, as they are often found in commercially available furanosyl and pyranosyl materials, and some of them contain more than one O-isopropylidene groups. Methods that permit regioselective removal of O-isopropylidene groups are extremely valuable, as the number of steps in the total synthesis of complex oligosaccharides could be significantly decreased. Here we report that trifluoroacetic acid (TFA)/acetic anhydride (Ac₂O) can be used to regioselectively convert one of the two O-isopropylidene groups to vicinal di-O-acetates in the di-O-isopropylidene-protected galacto- and fructo-pyranosyl systems, and the reagent is compatible with some common functionalities such as sulfonate esters, bromide, azide etc.

Diazepinium perchlorate: a neutral catalyst for mild, solvent-free acetylation of carbohydrates and other substances

Diazepinium perchlorate-promoted acetylation of free as well as partially protected sugars, phenols, thiophenols, thiols, other alcohols and amines is described.

Synthesis and antitumor activity of novel 2',3'-diethanethio-2',3',5'-trideoxy-5'-triazolonucleoside analogues

A series of novel 2',3'-diethanethio-2',3',5'-trideoxy-5'-triazoloribonucleosides was synthesized in excellent yields and their antitumor activity was evaluated. These nucleoside analogues with aromatic substituted triazole rings showed significantly improved activity towards a broad range of tumor cell lines and those without arene substitutes were inactive.