16159
Compounds 1 - 4 had unprecedented isospongian diterpene skeletons with a trans - anti - cis fused tricyclic ring system .
 Chemical: isospongian diterpene
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: isospongian diterpene