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