Synthesis and Biological Evaluation of New Acinetoferrin Homologues for Use as Iron Transport Probes in Mycobacteria

Abstract

Four new acinetoferrin homologues were synthesized using a modular synthetic approach. Two linear and two cyclic imide derivatives were generated and evaluated for growth stimulating behavior in Mycobacterium avium subsp paratuberculosis. The yield for the tandem coupling of a functionalized aminohydroxamic acid motif (2 equiv) to a tert-butyl citrate derivative was significantly improved using DCC and N-hydroxysuccinimide. (1)H NMR spectroscopy (CD(3)OD) provided a convenient method for monitoring the final imidization step in TFA using the doublet patterns between 2.5 and 3.06 ppm. New protocols demonstrated that only a 20% growth enhancement was observed with M. avium subsp. paratuberculosis using the imide of acinetoferrin. Last, a siderophore from Streptomyces pilosus, deferrioxamine B, was shown to cross-feed M. avium subsp. paratuberculosis with the same efficiency as the more costly, native chelator, mycobactin J.