C-Glycosylation of naphthols using glucosyl donors

Abstract

Attempts to effect direct C-glycosylation of naphthols 6, 7, and 8 using glucosyl donors 9 and 10 were unsuccessful. O-Glycosides 11, 12 and 15 were obtained under Mitsunobu conditions, however, these failed to undergo rearrangement to the C-glycosides 13, 14 and 16, respectively. Successful C-glycosylation of naphthols 7 and 8 was realized using the more reactive 2-deoxyglucosyl acetate donor 18 with trimethylsilyl triflate and silver perchlorate as the Lewis acid promoters. Use of acetonitrile as solvent formed the C-glycosides 20 and 22 in preference to the corresponding O-glycosides 19 and 21, respectively.