Myxochelins B, C, D, E and F: A New Structural Principle for Powerful Siderophores Imitating Nature

The synthesis of the natural siderophore myxochelin B (1S) and its enantiomer 1R is described. 1S and 1R served as precursors for the synthesis of new hexadentate siderophores, the myxochelins C (7S) and CR (7R), D (14S) and DR (14R), E (19S) and (RS)-F (26R, S), with 2,3-dihydroxybenzoate (DHB) ligands and the simple backbones of asymmetric 1,2,n-triamino-n-alkanes. For the myxochelins C, D, E and F n is 6 (from lysine), 5 (from ornithin), 4 (from asparagine amide) and 7 [from (±)-2-aminopimelic acid], respectively. The additional amino functions in the starting compounds were provided by dehydration of the corresponding primary amides, and subsequent reduction of the nitriles by cobalt boride in methanol. All new siderophores supply bacteria with ferric ions with an efficiency which depends on their chain length and stereochemistry. They show significant activity against the cytomegalo virus.