21080
Recently we reported the synthesis and structure - activity study of endomorphin - 1 ( EM - 1 ) analogues containing novel , unnatural alpha - methylene - beta - aminopropanoic acids ( Map ) .
 endomorphin - 1, EM - 1, alpha - methylene - beta - aminopropanoic acids, Map
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 endomorphin - 1, EM - 1, alpha - methylene - beta - aminopropanoic acids, Map