To investigate the biosynthetic pathway of IC202C, a potent immunosuppressive siderophore produced by Streptoalloteichus sp. 1454-19 with low yield limiting in vivo evaluation, we isolated a new compound IC202D and proferrioxamine Glt from the fermentation broth. IC202D was characterized as an aldehyde-containing analog of IC202C, and its conversion to IC202C via hydroxylamine treatment was confirmed. Feeding experiments using 15N-L-lysine (a precursor of cadaverine) and 13C-succinic acid showed that L-lysine and succinic acid were incorporated into IC202C. 15N incorporation into both amide and hydroxamate groups indicated that N-hydroxylation occurred after the decarboxylation of L-lysine to cadaverine. Additionally, 15N incorporation into the aldoxime moiety suggested that IC202C was not derived from IC202D. Based on these results, we proposed a biosynthetic pathway for IC202C involving the condensation of 3 moles of cadaverine (from L-lysine decarboxylation) and 2 moles of succinic acid to form the skeleton, followed by N-hydroxylation and formation of the aldoxime from terminal amine precursors.