Carbohydrates, fluorinated, hydrogen bonding

The biochemical rationale for incorporating fluorine in the carbohydrate residue is that replacement of a hydroxyl by fluorine would cause only a very minor steric perturbation of the structure or conformation while at the same time would have a profound electronic effect on neighboring groups. The substitution is possible while retaining the capacity of the position as an acceptor in hydrogen bonding. Yet these same attributes make the synthesis of fluorinated carbohydrates difficult. The synthesis of fluorinated carbohydrates offers a particularly fruitful field for the combination of modem chemical and enzymatic synthetic techniques. Total synthesis would be difficult because of the stereochemical control required at the multiple adjacent asymmetric centers of a fluorinated carbohydrate (105). 

The natural occurrence of the C-F bond in carbohydrates is restricted to nucleocidin, an antibiotic in which the hydrogen at C-4 of this ribofuranoside is replaced by fluorine. In contrast, during the last 10 years, new synthetic methods for the introduction of both and F into carbohydrates have led to an explosive growth in the number and variety of fluorinated sugars. Therefore, compounds that were relatively rare have become readily accessible for chemical and biochemical research. 

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