Phenyliodine Bis(trifluoroacetate) (PIFA) as an Excellent Promoter of 2‐Deoxy‐2‐phthalimido‐1‐thioglycosides in the Presence of Triflic Acid in Glycosylation Reactions

Abstract

AbstractA combination of phenyliodine bis(trifluoroacetate) (PIFA) and trifluoromethanesulfonic acid was found to be an effective activator for the glycosylation reaction, of which the glycosyl donor was p‐(octyloxy)phenyl 3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐1‐thio‐D‐glucopyranoside or p‐(octyloxy)phenyl 3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐1‐thio‐D‐galactopyranoside. The reaction proceeded with good yields when naturally occurring and derived alkanols, such as cholestanol, (–)‐menthol, 1‐ and 2‐adamantanols and nor‐kauranol, were employed as acceptor substrates. Interestingly, the glycosylation reaction of sterically hindered terpenoid alcohols, such as (–)‐ and (+)‐borneols and (+)‐fenchyl alcohol, with p‐(octyloxy)phenyl 3,4,6‐tri‐O‐acetyl‐2‐deoxy‐2‐phthalimido‐1‐thio‐D‐glucopyranoside afforded the desired β‐glycoside in quantitative yield. Moreover, the present reaction was useful to synthesize disaccharides of which the non‐reducing end was composed of a D‐glucosamine or D‐galactosamine unit.