20 R= H the 3'-and 5'-hydroxyl groups are required for good substrate activity. While the 5'- hydroxyl group must be retained in order to allow phosphorylations to the 5'-triphosphate, the 3'-hydroxyl may be replaced by other functions which mimic that functional group. One of the most favored replacements in carbohydrates is a fluorine atom" which is strongly electronegative but sterically undemanding. Since fluorine has approximately the same ...
![1-[(2R,5S)-3-Fluoro-5-(hydroxymethyl)-2,5-dihydro-2-furanyl]-2,4( 1H,3H)-pyrimidinedione结构式](https://image.chemsrc.com/caspic/155/122757-52-2.png)
