Glycosidation with 1-Hydroxy Sugars as Glycosyl Donors Promoted by Trimethylsilyl Chloride and Zinc Triflate.

A New Route toexo-Glycals Using the Ramberg−Bäcklund Rearrangement

“…Our initial studies, which were designed to explore the scope of the aglycon in our methodology, were conducted on benzyl‐protected glucose derivatives (Scheme , a, and Table 1). Commencing with tetra‐ O ‐benzyl‐ D ‐glucose ( 1 ), thioglycosylation with a variety of thiols was accomplished using a modification of Suzaki’s zinc triflate‐mediated procedure21 to prepare S ‐glycosides 2b−h as mixtures of α‐ and β‐anomers, which were separated and characterised individually. For the preparation of the methyl thioglycosides 2aα and 2aβ , the method reported by Landry and co‐workers19 using dimethyl disulfide was employed in order to avoid handling the toxic and volatile (b.p.…”

“…The thioglycosides 2i and 2j were prepared from peracetylated galactose ( 4 ) and mannose ( 5 ), respectively, by boron trifluoride‐mediated thioglycosylation, followed by deacetylation and benzylation (Scheme 2, b and c). Thiocellobioside 2k was prepared from the corresponding acetyl‐protected glycosyl bromide according to the method of Durette and Shen,22 and thioriboside 2l was prepared from 2,3,5‐tri‐ O ‐benzyl‐ D ‐ribofuranose23 ( 6 ) by using Suzaki’s method (Scheme 2, d and e) 21. Sulfur oxidation of these derivatives was achieved in most cases by reaction with Oxone ® in aqueous acetone to give the corresponding sulfones 3 .…”

Synthesis of Benzodioxane and Benzofuran Scaffolds Found in Neolignans via TMS Triflate Mediated Addition to 1,4-Benzo­dioxane Hemiacetals

“…To convert the acetals and hemiacetals to the activated oxonium ion, a combination of TMSCl and Zn(OTf) 2 was employed, using a procedure reported by Susaki. 17 When the aryl addition reactions were attempted with acetals 40 and 41, only starting material was returned. Unexpectedly, when the addition of trimethoxybenzene was attempted using TMSCl and Zn(OTf) 2 with hemiacetal 42, instead of the expected 1,4-benzodioxane 44, benzofuran 45 was produced as the sole product of the reaction in 56% yield (Scheme 10).…”

The glycosylation of steroids

“…141 Suzaki demonstrated that another combination comprising a mixture of TMSCl and a catalytic amount of Zn(OTf) 2 in CH 2 Cl 2 was a more efficient promoter of glycosylation than TMSOTf. 166 The results concerning the glycosylation of 3b-cholestanol with various 1-hydroxy sugars are collected in Table 31.…”