L-Leucine, N-[[[6-[[[[2-(carboxyamino)ethyl]amino]carbonyl]amino]hexyl]amino]carb onyl]-b-alanyl-L-leucyl-L-arginyl-L-alanyl-L-leucyl-L-leucyl-L-arginyl-L-alanyl- L-leucyl-L-leucyl-L-arginyl-L-alan