DTLET;DELTAKEPHALIN;TYR-D-THR-GLY-PHE-LEU-THR;[D-Thr2,Leu5]enkephalyl-Thr;(D-THR2)-LEU-ENKEPHALIN-THR;(D-THR2)-LEU-ENKEPHALIN-THR-OH;H-TYR-D-THR-GLY-PHE-LEU-THR-OH;[D-Thr2]-Leucine enkephalin-Thr;L-Tyr-D-Thr-Gly-L-Phe-L-Leu-L-Thr-OH;[D-Thr2]-Leucine enkephalin-Thr acetate salt