Siderophores from the Entomopathogenic Fungus .

We report NMR- and MS-based structural characterizations of siderophores and related compounds from (Balsamo-Crivelli) Vuillemin, including ten new chemical entities (-, -, -, and ) and five known compounds, (, , , , and ). The siderophore mixture from ARSEF strain #2680 included two compounds in which -mevalonyl--hydroxyornithine replaces both () or one () of the -anhydromevalonyl--hydroxyornithine units of dimerumic acid (). Mevalonolactone () was present as a degradation product of and . ARSEF #2860 also produced compounds that have mannopyranose () or 4--methyl-mannopyranose units (, ), two compounds (, ) that can be rationalized as 4--methyl-mannopyranosyl analogues of the esterifying acid moieties of metachelins A and B, respectively, and two probable decomposition products of , a nitro compound () and a formate (). Beauverichelin A (), a coprogen-type siderophore that represents the di-4--methyl-mannopyranosyl analogue of metachelin A, was detected in crude extracts of ARSEF #2860, but only in trace amounts. ARSEF strains #252 and #1955 yielded beauverichelin A in quantities that were sufficient for NMR analysis. Only the di- (-) and trihydroxamate () siderophores showed iron-binding activity in the CAS assay and, when ferrated, showed strong ESIMS signals consistent with 1:1 ligand/iron complexes.