R2 is {HEAD ~ hydrogen}, nitro, {TAIL ~ amino} or mono or dialkylamino; and 
R2 is { HEAD ~ hydrogen } , nitro , { TAIL ~ amino } or mono or dialkylamino ; and
OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH