In {TAIL ~ such compounds} {HEAD ~ R4} can be hydrogen, a lower alkyl group, such as a methyl or ethyl group; or generally any other group such as amino which does not generate steric hindrance or interference when coupled to the nitrogen atom along with the R3 group 
In
In { TAIL ~ such compounds } { HEAD ~ R4 } can be hydrogen , a lower alkyl group , such as a methyl or ethyl group ; or generally any other group such as amino which does not generate steric hindrance or interference when coupled to the nitrogen atom along with the R3 group
REL TAIL TAIL TAIL TAIL TAIL TAIL HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH