Neighboring-group participation sugars

Neighboring-group participation reactions by sulfur and nitrogen functions have also been observed for deoxyhalogeno sugars. An example is the formation of the anhydride 146, which possesses an oxathiabicyclo[2.2.2]octane ring-system constrained in a boat-like conformation, on treatment of methyl 4-0-benzoyl-2-S-benzoyl-6-bromo-6-deoxy-2-thio-Q -D-altropyranoside (145) with methanolic... 

The high a-selectivity is based on the absence of neighbor group participation. Protection of sugar 5 with acetyl groups and using the same epoxidation protocol leads to a 1 1 a ft mixture of the epoxides. 

Goodman, Leon, Neighboring-group Participation in Sugars, 22, 109—175... 

Goodman, L, Neighboring-group participation in sugars, Adv. Carbohydr. Chem. Biochem., 22, 109-175, 1967. 

---