Abstract A class of compounds with a common thiazolo [3, 2-a] pyrimidinone motif has been developed as general inhibitors of Bcl-2 family proteins. The lead compound was originally identified in a random screening of a small compound library using a fluorescence polarization-based competitive binding assay. Its binding to the Bcl-x L protein was further confirmed by 15 N-HSQC NMR experiments. Structural modifications on the lead ...