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In apolar solvents this tetraurea calix [ 4 ] arene 5 forms regioselectively a single hydrogen - bonded homodimer , from which the bis [ 2 ] catenane 10a is formed in 49 % by a metathesis reaction followed by hydrogenation .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Anatomy 
Text: {0} 
Answer:
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