Invited Review Chemoenzymatic Transformations in Nucleoside Chemistry

During the last quarter of the century almost no other aspect of organic synthesis has received as much attention as the preparation of enantiomerically pure compounds. The synthesis of optically active materials is an important task and represents a challenge to synthetic organic chemists. Increasing interest in the understanding of biological processes and the general recognition that chirality plays a crucial role in nature fostered a tremendous effort in enantioselective synthesis . Nowadays, the choice of a racemic synthesis over the development of an enantiopure compound must be justified, since opposite enantiomers interact differently within an organism and can display various activities . Thus, each country requires investigation into the bio-availability and pharmacological effect of a new chiral drug, and its final approval is based on complete background information for each enantiomer. The chemistry of natural nucleosides and their analogues has been thoroughly studied due to their potential as fungicidal, antitumour, and antiviral agents [1]. Consequently, extensive modifications have been made to both the heterocyclic base and the sugar moiety in order to avoid the drawbacks shown by nucleosides or analogues in certain applications. Since the late eighties, nucleoside analogue s have been investigated with renewed urgency in the search for agents effective against the Human Immunodeficiency Virus (HIV), the causative agent of AIDS. More effective treatment has also been sought for other viral infections, in particular those caused by Herpes Simplex Virus (HSV types 1 and 2), Varicella Zoster Virus (VZV), Human Cytomegalovirus (HCMV), and Epstein-Barr Virus