alternatively, when two Rc groups are attached to adjacent carbon atoms, together with the carbon atoms to which they are attached they form a 5–6 membered carbocyclic or heterocyclic ring D consisting of carbon atoms, 0–2 heteroatoms selected from {HEAD ~ the group} consisting of N, O, and {TAIL ~ Sp}, and 0–3 double bonds 
alternatively , when two Rc groups are attached to adjacent carbon atoms , together with the carbon atoms to which they are attached they form a 5–6 membered carbocyclic or heterocyclic ring D consisting of carbon atoms , 0–2 heteroatoms selected from { HEAD ~ the group } consisting of N , O , and { TAIL ~ Sp } , and 0–3 double bonds
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH