A novel method for stereoselective glycosidation with thioglycosides: Promotion by hypervalent iodine reagents prepared from PhIO and various acids

• Published in: Tetrahedron 1996-03, Vol.52 (11), p.3897-3904
• Main Authors: Fukase, Koichi, Kinoshita, Ikuko, Kanoh, Takeshi, Nakai, Yoshihiko, Hasuoka, Atsushi, Kusumoto, Shoichi
• Format: Article
• Language: English
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(96)00057-9

Combinations of iodosobenzene (PhIO) and various acids effectively promote glycosidation using thioglycosides as glycosyl donors. β-Selective glucosidation was effected by use of TfOH, Tf 2O, TMSOTf, Sn(OTf) 2, and Yb(OTf) 3 as catalysts with 2- O-benzoylated or 2- O-benzylated donors by virtue of either the neighboring group participation or the solvent effect of acetonitrile, respectively. Combinations of PhIO with SnCl 2-AgClO 4, SnCl 4-AgClO 4, BiCl 3-AgClO 4, and SbCl 3-AgClO 4 in ether were advantageous for α-glucosidation, where 2,2,2-trichloroethoxycarbonyl group introduced at the 6-position of a 2- O-benzylated donor remarkably increased α-selectivity. Combinations of PhIO and various acids effectively promote glycosidation using thioglycosides. β-Selective glucosidation was effected by use of TfOH, Tf 2O, TMSOTf, Sn(OTf) 2, and Yb(OTf) 3 as catalysts with 2- O-benzoylated or 2- O-benzylated donors by virtue of either the neighboring group participation or the solvent effect of acetonitrile, respectively. Combinations of PhIO with SnCl 2-AgClO 4, SnCl 4-AgClO 4, BiCl 3-AgClO 4, and SbCl 3-AgClO 4 in ether were advantageous for α-glucosidation.