19474
The 4 - aryl - 2 - thioxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines ( 33 - 38 ) and 4 - aryl - 2 - oxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines ( 39 - 41 ) were more efficiently resolved than the racemic 4 - aryl - 1 , 4 - dihydropyridines on the tetraproline chiralstationary phase .
 4 - aryl - 2 - thioxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines, 4 - aryl - 2 - oxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines, racemic 4 - aryl - 1 , 4 - dihydropyridines, 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 - 2 - thioxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines, 4 - aryl - 2 - oxo - 1 , 2 , 3 , 4 - tetrahydropyrimidines, racemic 4 - aryl - 1 , 4 - dihydropyridines, tetraproline