A NOVEL METHOD FOR STEREOSELECTIVE GLYCOSIDATION WITH THIOGLYCOSIDES - PROMOTION BY HYPERVALENT IODINE REAGENTS PREPARED FROM PHIO AND VARIOUS ACIDS

Combinations of iodosobenzene (PhIO) and various acids effectively pro mote glycosidation using thioglycosides as glycosyl donors. beta-Selec tive glucosidation was effected by use of TfOH, Tf(2)O, TMSOTf, Sn(OTf )(2), and Yb(OTf)(3) as catalysts with 2-O-benzoylated or 2-O-benzylat ed donors by virtue of either the neighboring group participation or t he solvent effect of acetonitrile, respectively. Combinations of PhIO with SnCl2-AgClO4, SnCl4-AgClO4, BiCl3-AgClO4, and SbCl3-AgClO4 in eth er were advantageous for alpha-glucosidation, where 2,2,2-trichloroeth oxycarbonyl group introduced at the 6-position of a 2-O-benzylated don or remarkably increased alpha-selectivity.