Nucleobases and their Analogs

　Nucleobases, usually simply called “bases”, are a vital sense component of DNA and RNA. The bases can be divided into two groups based on the structure: purines such as adenine and guanine; and pyrimidines such as cytosine, thymine and uracil. Other nucleobases can be created by the modifi cation of these basic structures. For example, hypoxanthine and xanthine are generated in living systems through deamination of adenine and guanine, respectively. Furthermore, nucleobase analogue 5-fluorouracil (5-FU) is used as an anticancer agent. Derivatives of 2-fluoroadenine have been widely reported as prodrug forms of anticancer agents.