Fig. 1.

Decomposing organic compounds into molecular fragments. Assuming that organic compounds are composed of sets of rigid fragments connected by flexible linkers, a molecule can be decomposed into its building blocks tracking the atomic connectivity. a A stick representation of afatinib. Extracting rigid fragments: b all rigid fragments are shown as thick lines, c only those rigid fragments composed of four or more atoms are retained. Extracting flexible linkers: d small fragments connected by rotatable bonds, e small linkers are merged to form longer fragments, a single atom can act as a linker as well. The following colors are used for atom types: carbon—green, nitrogen—blue, oxygen—red, fluorine—yellow, and chlorine—pink