Gold(III) Chloride and Phenylacetylene: A Catalyst System for the Ferrier Rearrangement, and O‐Glycosylation of 1‐O‐Acetyl Sugars as Glycosyl Donors

Abstract

We have developed a new catalyst system comprising AuCl3 and phenylacetylene that promotes the Ferrier rearrangement of glycals and 2‐acetoxymethylglycals with different nucleophiles, and also the O‐glycosylation of 1‐O‐acetyl sugars to obtain a variety of useful glycosides at room temperature through relay catalysis. Good anomeric selectivity was observed for the Ferrier rearrangements, whereas the O‐glycosylation of 1‐O‐acetyl sugars gave mixtures of diastereomers with moderate to excellent selectivity.

Methods for 2-Deoxyglycoside Synthesis

“…The combination of gold(III) chloride with phenylacetylene has also been devised by the Vankar group as a new relay catalytic system to promote the Ferrier rearrangement of acetyl-protected glycals and 2-acetoxymethylglycals as well as the O -glycosylation of 1- O -acetyl sugars with different nucleophiles. 355 Reaction times are short and the desired products were obtained in good to excellent yields and with high anomeric selectivity in the case of glycals, while moderate to good selectivities were observed for the 1- O -acetyl glycosyl donors 324 ( Scheme 90 ). Subsequently, the same group expanded the scope of the Au(III)-based relay catalytic system to glycosylations using glycosyl trichloroacetimidates 221 , which was shown to be more efficient than AuCl 3 alone.…”

AuIII‐Halide/Phenylacetylene‐Cata­lysed Glycosylations Using 1‐O‐Acetyl­furanoses and Pyranose 1,2‐Ortho­esters as Glycosyl Donors

“…In contrast, our method [15] to activate OAc as an anomeric leaving group needs only catalytic amounts of both AuCl 3 and phenylacetylene. As an extension of our work, we report in this paper O-glycosylation using 1-O-acetylfuranoses and 1,2-orthoesters using Au III halide catalysts with or without a phenylacetylene cocatalyst.…”

“…[14a] In this context, we recently reported [15] a new relay catalyst system comprising Au III chloride and phenylacetylene, which was able to activate 1-O-acetyl pyranoses as glycosyl donors and overcome these drawbacks. In this approach, AuCl 3 and phenylacetylene were both used in only catalytic amounts.…”

AuBr3-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

“…Gold(I) and gold(III) complexes are usually alkynophilic [ 2 ], carbophilic and oxophilic because of their affinity towards the alkynes’ and C–O π systems [ 3 – 6 ]. Thus, various research groups employed either a remote alkyne group possessing versatile glycosyl donors [ 7 – 16 ] or used glycals [ 17 ] for effective O -, C -, and S -glycosylation reactions using gold(I) and gold(III) catalysts. Among the gold-catalyzed activation of non-alkynic glycosyl donors, glycosyl halides [ 18 ], armed O -methyl glycosides [ 19 ], armed and disarmed thioglycosides [ 20 ] as well as trichloroacetimidate [ 21 – 22 ] donors were successfully applied to O - and C -glycosylations.…”