17422
In this study , we designed and synthesized nine new derivatives of 17 beta - estradiol ( E2 ) with a bulky side chain attached to its C - 7 alpha position , and determined their ER antagonistic activity using in vitro bioassays .
 Chemical: 17 beta - estradiol
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: 17 beta - estradiol