Boric acid derivatives as reagents in carbohydrate chemistry : Part IV. The interaction of phenylboronic acid with hexopyranoid compounds☆

Abstract Methyl β- d -glucopyranoside, like the α-anomer, racts smoothly with phenylboronic acid (1 mol) to give a 4,6-cyclic boronate which, with excess of reagent, forms a 2,3-pyroboronate. The nature of the products obtained from hexopyranoid derivatives which possess the d - lyxo -configuration at C- 3 , C- 4 and C- 5 was found to be dependent upon the substituents at C-1 and C-2. Whereas methyl α- and β- d -galactopyranoside, methyl 2-deoxy-β- d - lyxo -hexopyranoside, 1,5-anhydro- d -galacitol, and 1,5-anhydro-2-deoxy- d - lyxo -hexitol afforded 4,6-cyclic esters in good yield, the only products obtained from d -galactal and methyl 2-deoxy-α- d - lyxo -hexopyranoside possessed the 3,4-cyclic structures.