Recent advances in gold-catalyzed glycosylation - Carbohydrate Chemistry: Chemical and Biological Approaches - page 147

co-workers. 1,2-trans Ribofuranosides prepared by this protocol were
successfully converted into the challenging 1,2-cis arabinofuranosides by
sequential oxidation and reduction. These 1,2-trans and 1,2-cis fur-
anosidations were successfully applied as key steps to the synthesis of
hexasccharide 52 as major structural motifs in the cell wall of Myco-
bacterium tuberculosis (Scheme 10). 22
2.6 Gold(III)-catalyzed glycosidation with 1-ethynylcyclohexanyl
glycosyl donors
In 2012, after a systematic evaluation of the effect of the substitution
groups on the activation of substituted propargyl glycosides (manno-
pyranosyl, glucosyl and galactosyl donors) with gold catalyst, Hotha and
co-workers discovered that the use of gem-disubstituted donors, espe-
cially 1-ethynylcyclohexanyl glycolsyl donors (for example 53) increases
the reactivity and allows transglycosidation with sugar-based aglycones
at room temperature to produce corresponding disaccharides 54
(Scheme 11) in high yields. Thorpe-Ingold like effect accounts for the
increased reactivity of gem-disubstitution. 23
Scheme 10
Scheme 11