2,5-Piperazinedione, 3,6-bis(1-hydroxyethyl)-, (3S-(3alpha(S*),6alpha(S*)))- 54617-73-1 Cyclo(L-allothr)2 Cyclo(L-allothreonine)2 Cyclo(L-thr)2 Cyclo(L-thr-L-thr) Cyclo(L-threonine)2 Cyclo(di(thr)) Cyclo(di(threonine))