AuCl₃– and AuCl₃–Phenylacetylene‐Catalyzed Glycosylations by Using Glycosyl Trichloroacetimidates

Abstract

Abstract Glycosylations of armed and disarmed trichloroacetimidate‐based glycosyl donors were carried out by using the AuCl 3 –phenylacetylene relay catalyst system. The effectiveness of this catalytic system was also compared with that of using AuCl 3 alone as a catalyst. Glycosylations with these catalysts proceeded efficiently at room temperature within 5–45 min. Excellent diastereoselectivity was obtained for the glycosylation of 2‐ O ‐acetyl‐protected disarmed glycosyl donors, whereas armed glycosyl trichloroacetimidates gave rise to a mixture of anomeric glycosides. Acid‐sensitive nucleophiles such as Fmoc‐serine tert ‐butyl ester or Fmoc‐threonine tert ‐butyl ester successfully underwent the glycosylations, albeit in moderate yields, under mild conditions at room temperature.