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 the group consisting of N, O, and {HEAD ~ Sp}, and {TAIL ~ 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 the group consisting of N , O , and { HEAD ~ Sp } , and { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL