We developed a new artificial DNA triplex triad which has the adenine nucleobase in the first strand. This triplex triad (A-psi-C*) is composed of adenine, pseudouridine and 5-sudstituted cytosine as the 1st, 2nd and 3rd strand nucleobases, respectively. The molecular design and synthesis of the nucleobases for the 2nd and 3rd strand of the triplex are also described.