15H-Pyrrolo[2,1-f][1,15,4,7,10,20]dioxatetraaza cyclotricosine, cyclic peptide deriv Leucine, N-[1-[N-[4-[[3-hydroxy-4-[[N-[N-[1-(2-hydroxy- 1-oxopropyl)prolyl]-N-methylleucyl]threonyl]amino]- 5-methyl-1-oxooctyl]oxy]-2,5-dimethyl-1,3-dioxohexyl]leucyl]prolyl]-N-methyl-, .phi.-lactone, stereoisomer NSC685703