Synthesis and glycosylation of a series of 6-mono-, di-, and trifluoro S-phenyl 2,3,4-tri-O-benzyl-thiorhamnopyranosides. Effect of the fluorine substituents on glycosylation stereoselectivity.
A series of 6-mono-, di-, and trifluoro analogs of S-phenyl 2,3,4-tri-O-benzyl-D- or L-thiorhamnopyranoside has been synthesized and used as donors in glycosylation reactions, with activation by the 1-benzenesulfinyl piperidine/triflic anhydride system. The stereochemical outcome of the glycosylation reactions was found to depend on the electron-withdrawing capability of the disarming substituent at the 6-position, i.e., on the number of fluorine atoms present. The results are explained with regard to the increased stability of the glycosyl triflates, shown to be intermediates in the reaction by low-temperature 1H NMR experiments, with increased fluorine content.
Crich
David
D
Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA. dcrich@chem.wayne.edu
Vinogradova
Olga
O
D001597:Benzylidene Compounds / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005461:Fluorine / Q000737:chemistry*; D005663:Furans / Q000737:chemistry*; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010880:Piperidines / Q000737:chemistry*; D012210:Rhamnose / Q000031:analogs & derivatives / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013449:Sulfonamides / Q000737:chemistry*; D013865:Thioglycosides / Q000138:chemical synthesis*
D001597:Benzylidene Compounds; D005663:Furans; D010880:Piperidines; D013449:Sulfonamides; D013865:Thioglycosides; D005461:Fluorine; C032727:piperidine; C474725:triflic anhydride; D012210:Rhamnose