The present invention relates to a compound having a structure analogous to firefly luciferin. In particular, the invention relates to a heterocycle compound which produces a luminescence at a light wavelength different from that of firefly luciferin in nature. The present invention provides a heterocycle compound of following general formula I. In the above general formula, R
1
, R
2
and R
3
can be each independently H or C
1-4
-alky. In the above general formula, X and Y can be each independently C, N, S or O. In the above general formula, the olefin chain part expressed as “n” can be changed to desired length.