A novel lipopeptide antibiotic, stalobacin I (1), was discovered from a culture broth of an unidentified Gram-negative bacterium. Stalobacin I (1) had a unique chemical architecture composed of an upper and a lower half peptide sequence, which were linked via a hemiaminal methylene moiety. The sequence of 1 contained an unusual amino acid, carnosadine, 3,4-dihydroxyariginine, 3-hydroxyisoleucine, and