Path to take when labeling R/S
The compound you are presenting is a natural product, compactin. The numbers of the carbon atoms are arbitrary. The digraph of C9 shows how the configuration is determined. Sphere 2 contains the atoms C8, C10, C14 and H. Clearly, hydrogen has the lowest priority. Sphere 3 has the locants C10{15,5,H}, C8{7,(7),H} and C14{H,H,H}. In a one-to-one comparison of the locants, C10 and C8 have priority over C14 because C&gt;H. So C14 has the next lowest priority. C(7), which is a duplicate atom of atomic number 6, is attached to three atoms in sphere 4 of atomic number zero. Zero is as low as you can go. Therefore, the priorities are C10&gt;C8&gt;C14&gt;H. C9 has the (S)-configuration.