wherein X is carbon or nitrogen and can be at {TAIL ~ any position} in {HEAD ~ the ring}, and 
wherein X is carbon or nitrogen and can be at { TAIL ~ any position } in { HEAD ~ the ring } , and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH