15H-Pyrrolo[2,1-f][1,15,4,7,10,20]dioxatetraazacyclotri- cosine, cyclic peptide deriv. 77327-05-0 DIDEMNIN B L-Tyrosine, N-[1-[N-[4-[[3-hydroxy-4-[[N-[N-[1-(2-hydroxy-1-oxopropyl)- L-prolyl]-N-methyl-L-leucyl]-L-threonyl]amino-5-methyl- 1-oxoheptyl]oxy]-2,5-dimethyl-1,3-dioxohexyl]-L-leucyl]- L-prolyl]-N,O-dimethyl-, .phi.-lactone NSC325319