title: A mild acetolysis procedure for the regioselective removal of isopropylidene in di-O-isopropylidene-protected pyranoside systems.
abstract: 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.
authors.affiliation: Alberta Glycomics Centre, Department of Chemistry, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Alberta Glycomics Centre, Department of Chemistry, University of Calgary, Calgary, Alberta, T2N 1N4, Canada. Electronic address: ccling@ucalgary.ca.
authors.forename: Chang-Chun
authors.initials: CC
authors.lastname: Ling
mesh_terms: D000085:Acetates / Q000737:chemistry; D000089:Acetic Anhydrides / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry* / Q000302:isolation & purification*; D002236:Carbohydrate Conformation; D005463:Fluoroacetates / Q000737:chemistry; D008958:Models, Molecular; D009844:Oligosaccharides / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000085:Acetates; D000089:Acetic Anhydrides; D000475:Alkenes; D005463:Fluoroacetates; D009844:Oligosaccharides; C017958:trifluoroacetic anhydride; C013658:propylene
keywords: Acetolysis; Isopropylidene; Pyranosides; Regioselective deprotection; Trifluoroacetic acid