Library generation through successive substitution of trichlorotriazine.

The decreasing reactivity of tri-, di- and monochlorotriazine was utilized for the solid-phase construction of a combinatorial library with three randomized positions, using 20 amino acids and 50 amines as building blocks. The first chlorine atom was selectively substituted by coupling a large excess of trichlorotriazine to the support-bound amino acid, thus avoiding simultaneous substitution of the second chlorine. The second and third diversity positions were selectively introduced by coupling amines at different temperatures. Mixtures of model compounds were synthesized and analyzed, showing the correct representation of all expected components. A library composed of 12,000 compounds was generated using this method.