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It was therefore decided to further functionalize this side chain through reactions with the terminal carboxylic acid in an effort to enhance the interaction with the DNA phosphate backbone and improve the anti - cancer activity .
 Chemical: carboxylic acid; Chemical: phosphate
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: carboxylic acid; Chemical: phosphate