{HEAD ~ Cyclic lactones} having {TAIL ~ a closed ring structure} containing six members can also be employed, if desired, such as lactide or glycolide 
having
{ HEAD ~ Cyclic lactones } having { TAIL ~ a closed ring structure } containing six members can also be employed , if desired , such as lactide or glycolide
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH