11417
Optimization of the 4 - R substituent in 1 led to ethyl and isopropyl analogs 1e and 1f with 1 - 7 nM potency towards both the wild - type virus and a Tyr181C variant .
 Chemical: ethyl; Chemical: isopropyl
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: ethyl; Chemical: isopropyl