21219
We demonstrate the difficulty of realising a phosphorylation step on the anomeric position of 2 - deoxyribose , and we discover that introduction of fluorine atoms on the 2 position of 2 - deoxyribose enables the phosphorylation step : in fact , the stability of the prodrugs increases with the degree of 2 - fluorination .
 Chemical: 2 - deoxyribose; Chemical: fluorine; Chemical: 2 - deoxyribose
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: 2 - deoxyribose; Chemical: fluorine; Chemical: 2 - deoxyribose