R1 and R2 are independently H, C1 C18 alkyl; or R1 in {HEAD ~ combination} with {TAIL ~ R2 forms} a saturated 5 or 6 membered heterocycle that is a piperidine, a morpholine, a pyrrolidine or a piperazine 
R1 and R2 are independently H , C1 C18 alkyl ; or R1 in { HEAD ~ combination } with { TAIL ~ R2 forms } a saturated 5 or 6 membered heterocycle that is a piperidine , a morpholine , a pyrrolidine or a piperazine
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH