The main subject in our laboratory is the total synthesis of complex natural products. Recently, we are also working on the development of unique photoreactive organic molecules by utilizing the knowledge and technology for synthesizing complex natural products. For example, we discovered for the first time that the 1,3a,6a-triazapentalene (TAP) skeleton is an excellent fluorescent chromophore, and we have established the efficient method for the synthesis of TAPs. This synthetic method supplied various TAP derivatives that change the color and intensity of the fluorescence by reacting with smelly methanethiol in the breath, emit fluorescence in response to the mechanical stimuli, or serve as the most compact fluorescence labeling reagent. In addition, some TAP derivatives are already commercially available as reagents for fluorescently staining live cells. The practical application of TAP derivatives that serve as periodontal disease sensors and the development of photoreactive reagents for phototherapy are currently underway in our laboratory.​