The chemistry of unprotected sucrose: the selectivity issue

Some basic principles of the chemistry of unprotected sucrose, the most abundant pure organic molecule produced, are described. The relationships between the structure of sucrose in Solution and the selectivity of its chemical transformations are emphasized. Using a selection of examples, it is demonstrated that the simple primary alcohol vs secondary alcohol order of reactivity cannot serve as a general rule for describing the relative reactivity of sucrose's eight hydroxyl groups. Depending oil the reaction conditions (solvent, electrophilic reagent, catalysis...) the nucleophilic behaviour of sucrose changes, leading to compounds Substituted at different positions. Some specific positions, OH-2, 1' and 3', close to anomeric carbon atoms and involved in intramolecular hydrogen bonds, play all as important role in this chemistry as the primary OH-6 and 6', whereas enzymatic catalysis leads to OH-1' substituted derivatives. The synthesis of amphiphilic derivatives, in which the carbohydrate moiety serves as the hydrophilic part, is notably described. The use of aqueous media for Sucrose chemistry is also discussed, showing that even water-sensitive electrophilic substrates can be used. (C) 2004 Academie des sciences. Published by Elsevier SAS. All rights reserved.