Differential reactivity of α- and β-anomers of glycosyl accepters in glycosylations.: A remote consequence of the endo-anomeric effect?

[GRAPHICS] When phenyl tri-O benzyl-1-thio-beta-D-galactopyranosid acid esters were coupled with a 1/1 mixture of alpha and beta 2,3 di-O-protected D-galactopyranosiduronic acid esters, the beta-anomer proved to be more reactive, Data from theoretical calculations suggested that the enhanced reactivity of this anomer compared with the a one would be due to a stronger hydrogen bond of the C-4 OH with the ring oxygen.