29577
Design , synthesis and molecular modeling of novel pyrido [ 2 , 3 - d ] pyrimidine analogs as antifolates : Application of Buchwald - Hartwig aminations of heterocycles .
 Chemical: pyrido [ 2 , 3 - d ] pyrimidine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
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Answer:
 Chemical: pyrido [ 2 , 3 - d ] pyrimidine