19471
Enantiomeric separation of racemic 4 - aryl - 1 , 4 - dihydropyridines and 4 - aryl - 1 , 2 , 3 , 4 - tetrahydropyrimidines on a chiral tetraproline stationary phase .
 4 - aryl - 1 , 4 - dihydropyridines, 4 - aryl - 1 , 2 , 3 , 4 - tetrahydropyrimidines, tetraproline
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 4 - aryl - 1 , 4 - dihydropyridines, 4 - aryl - 1 , 2 , 3 , 4 - tetrahydropyrimidines, tetraproline