title: Efficient selective preparation of methyl-1,2,4-tri-O-acetyl-3-O-benzyl-beta-L-idopyranuronate from methyl 3-O-benzyl-L-iduronate.
abstract: Methyl 1,2,4-tri-O-acetyl-3-O-benzyl-L-idopyranuronate 6beta/6alpha, prepared from methyl 3-O-benzyl-L-iduronate (4), is a key synthon in heparin/heparan sulfate synthesis. The 1H and 13C NMR spectra of the furanose-pyranose mixture of 4, after dissolution and equilibration in d(4)-methanol, were fully assigned allowing to expect that 4 could crystallise in the beta-pyranose form. New acetylation conditions able to trap this form were subsequently devised, allowing the isolation of 83% of pure 6beta by simple crystallisation, along with 9% of the 6beta/6alpha mixture. This represents a major advantage over the previously published procedure, especially on multigram scales.
authors.affiliation: Laboratoire de Chimie Organique Multifonctionnelle, UMR 8614 'Molecular Glycochemistry', Bat. 420 Université Paris Sud, F-91405, Orsay, France.
authors.forename: Anna
authors.initials: A
authors.lastname: Dilhas
authors.forename: David
authors.initials: D
authors.lastname: Bonnaffé
mesh_terms: D002236:Carbohydrate Conformation; D006493:Heparin / Q000737:chemistry; D007067:Iduronic Acid / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism; D013696:Temperature; D013997:Time Factors
chemical_list: C479525:methyl 1,2,4-tri-O-acetyl-3-O-benzylidopyranouronate; C479526:methyl 3-O-benzyliduronate; D007067:Iduronic Acid; D006493:Heparin