l-Nucleosides as chemotherapeutic agents

Nucleoside analogues have been the cornerstone of antiviral therapy over the past thirty years and, currently, 16 commonly used antiviral drugs belong to this category. Although for long time it was believed that only D-nucleosides, possessing a 'natural' stereochemistry, could elicit biological activity, in the last decade this has been proven not to be true. 3TC, a L-nucleoside analogue, is one of the most effective anti-HIV and anti-hepatitis B virus drugs, and nine other L-nucleosides are currently undergoing clinical trials and/or preclinical studies as antiviral or antitumoral agents. This minireview summarizes some biological features and the current status of these promising L-nucleoside analogues.