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To better understand the ligand - receptor interactions , a series of dicarboxylic ester - type of salvinorin A derivatives were synthesized and evaluated for their binding affinity at kappa - , delta - and mu - opioid receptors .
 Chemical: dicarboxylic ester; Chemical: salvinorin A
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: dicarboxylic ester; Chemical: salvinorin A