An imrpoved practical method for synthesis of aryl C-glycosides from unprotected methyl glycosides and 1-hydroxy sugars

Aryl C-glycosidations of the unprotected methyl glycosides 9-12 and the unprotected 1-hydroxy sugars 14 and 15 with 2-naphthol 6 using TMSOTf proceed much more effectively than those of the acylated methyl glycosides 4 and 5; the unprotected methyl glycoside 10 is also smoothly coupled with other phenol and naphthol derivatives 25-27 to give the corresponding unprotected o-hydroxyaryl β-C-glycosides in high yields (TMSOTf = trimethylsilyloxytrifluoromethanesulfonate).