The hydroxyl groups of glucose can be esterified with acetic anhydride. Similarly fructose can be acylated to form pentacetyl derivative.
Ester of phosphoric acid have special significance in biological chemistry since sugars are metabolized in phosphorylated form, e.g., glucose is phosphorylated to glucose – 6-phospate before it is oxidized. In hemiacetal forms OH group on C-1 id highly reactive and forms glucose -1-phosphate. 

Mild oxidizing agents, such as Fehling’s solutions (alkaline copper sulphate) and sodium hypoiodite (NaOI), and bennedict’s reagent oxidize aldoses to aldonic acids. Glucose is oxidized to gluconic acid.