title: Glycan ester deacylation by TBAOH or TBAF: regioselectivity vs. polysaccharide structure.
abstract: Tetrabutylammonium fluoride (TBAF) and tetrabutylammonium hydroxide (TBAOH) have been found to mediate regioselective deacylation of cellulose esters, with unexpected selectivity for removal of acyl groups at the more hindered secondary O-2/3 positions. This simple, efficient, one-step process triggers our investigation of TBAF/TBAOH deacylation on other glycan (amylose, curdlan, dextran, pullulan and glucomannan) esters to examine the generality of this reaction and the impact of glucan and glucomannan structure on deacylation regioselectivity. Remarkably regioselective O-2/3 deacylation was observed with amylose triesters, while moderately regioselective O-2/4 deacylation of curdlan triester occurred. No regioselectivity was observed with dextran triester, as predicted due to the lack of primary OH groups. We observed deacylation of pullulan and glucomannan triesters, but due to the complexity of the partially substituted products have not yet been able to determine the deacylation regioselectivity for these glycan esters.
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, United States.
authors.forename: Ruoran
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, College of Science, Virginia Tech, Blacksburg, VA 24061, United States.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Department of Biological Sciences, College of Science, Virginia Tech, Blacksburg, VA 24061, United States.
authors.forename: Joyce
authors.initials: J
authors.lastname: Kuang
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, United States; Department of Sustainable Biomaterials, College of Natural Resources and Environment, Virginia Tech, Blacksburg, VA 24061, United States. Electronic address: kjedgar@vt.edu.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Edgar
mesh_terms: D000085:Acetates / Q000737:chemistry; D004952:Esters; D005936:Glucans / Q000737:chemistry*; D007536:Isomerism; D008351:Mannans / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: D000085:Acetates; D004952:Esters; D005936:Glucans; D008351:Mannans; D000644:Quaternary Ammonium Compounds; C022901:(1-6)-alpha-glucomannan; C009405:tetrabutylammonium
keywords: Amylose; Deacylation; Glycan esters; Regioselectivity; TBAF; TBAOH