{HEAD ~ A process} 2, wherein R1, R2 and {TAIL ~ R3} are hydrogen and R4 is a lower alkyl group 
{ HEAD ~ A process } 2 , wherein R1 , R2 and { TAIL ~ R3 } are hydrogen and R4 is a lower alkyl group
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH