| abstract |
The compound according to the present invention is a compound represented by the following chemical formula: n n n n n n n n n n n n wherein, in the above-described chemical formula, R 1 is oxygen or sulfur, and R 2 to R 6 are each independently selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyl group having 1 to 6 carbon atoms and a nitro group. |