Substituents R1, R2, R3 and R4 have {HEAD ~ the same meaning} as defined in {TAIL ~ the specification} 
Substituents R1 , R2 , R3 and R4 have { HEAD ~ the same meaning } as defined in { TAIL ~ the specification }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL