14637
Interestingly and in contrast to previously described findings , ( S ) - 6 - guanidinopurine derivatives were generally more active than their ( R ) - counterparts .
 Chemical: ( S ) - 6 - guanidinopurine
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: ( S ) - 6 - guanidinopurine