| http://www.w3.org/ns/prov#value | - When Y2 is a carbon atom, b2 represents a double bond. [0063] In the formula (8), X201, X202, X203 and X204 each represent a nitrogen atom or C???R and forms a nitrogen-containing heteroaryl 6-membered ring with ???C???N???, with the proviso that at least one of X201, X202, X203 and X204 represents a nitrogen atom.
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