IRON UPTAKE SYSTEM OF SOME MEMBERS OF THE GENUS TOLYPOCLADIUM - CRYSTAL-STRUCTURE OF THE LIGAND AND ITS IRON(III) COMPLEX

A new type of fungal hydroxamic acid (1'S,2'R,4'S,6'R)-3-(2',4'-dimethyl-6'-vinylcyclohexyl)-1,4-dihydroxy-2(1H)-pyridone (tolypocin, HL) has been isolated from the mycelium of the fungus Tolypocladium geodes. The acid (C15H21NO3) crystallized from methanol [monoclinic, space group P2(1), Z = 4, a = 12.28(1), b = 9.958(5), c = 12.737(4) angstrom, beta = 94.91(5)-degrees]. The structure was solved by direct methods and refined to a final R value of 0.055 for 2393 unique observed reflections. The iron(III) tris-chelate complex of this ligand [FeL3] has been isolated from the mycelium of the fungus Tolypocladium terricola. Its methanol solvate (C45H60FeN3O9.2MeOH) was crystallized from methanol [orthorhombic, space group P2(1)2(1)2, Z = 4, a = 20.27(3), b = 19.35(5), c = 13.43(4) angstrom]. The structure was solved by direct methods and refined to a final R value of 0.062 for 5562 observed reflections. The absolute configuration of the complex as determined from CD spectra and anomalous X-ray dispersion has been shown to be A-cis both in solution and in the solid state.