3-hydroxy-4(1H)-pyridinone-containing linear and cyclic hexapeptides and their iron(III) complexes - Synthesis, property, and the growth-promotion activity-

Linear and cyclic hexapeptides composed of epsilon-(3-hydroxy-1,4-dihydro-2 -methyl-4-oxo-1-pyridyl)-L,norleucine and glycine or P-alanine residue have been successfully synthesized. These hexapeptides formed 1:1 iron(III) com plexes at neutral pH region. Glycine linear (8a)- and beta -alanine cyclic hexapeptide (10)-iron(III) complexes predominantly existed in Delta -config uration, while P-alanine linear hexapeptide (8b)-iron(III) complex existed in Lambda -one. The relative stability constants of 8a, 8b, and 10-iron(III ) complexes were estimated to be 31.6, 33.4, and 31.7, respectively. From i ron(III) removal from human transferrin, linear hexapeptides (8a,b) were fo und to efficiently remove iron(III) compared with desferrioxamine B. The gr owth-promotion activity was also discussed.