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A series of F ( D ) LF ( D ) LF analogs has been synthesized , including either N - t - Boc or different N - ureido substituents .
 Chemical: N - t - Boc; Chemical: N - ureido
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: N - t - Boc; Chemical: N - ureido