The Bemis-Murcko scaffold analysis for 'centroids' (excluding non-cyclic molecules) resulted in 333 unique scaffolds out of 402, with 31 common scaffolds among 100 molecules. We further calculated the all-by-all Tanimoto similarities between molecules sharing common Bemis-Murcko scaffolds. The histogram of the lower triangular matrix (Fig. ) shows low similarity (less than 0.3) between most pairs. (Fig. ). Clustering allowed us to identify and select a diverse yet manageable subset of molecules that capture the key features of the larger data set.