STRUCTURES OF NEW PEPTIDE ANTIBIOTICS

hydroxyaspartic acid, D-a//o-threonine, D-serine, D-alanine and L-arginine. In plusbacins Bl ~ B4, one mole of L-/r<ms-3-hydroxyproline is replaced by L-proline. The fatty acid residue of At and Bt was determined to be 3-hydroxy-tetradecanoic acid, for A2 and B2 to be 3-hydroxy-isopentadecanoic acid, for A3 and B3 to be 3-hydroxy-isohexadecanoic acid, and for A4 and B4 to be 3-hydroxyhexadecanoic acid. A lactone linkage was suggested to reside between L-r/zre0-/?-hydroxyaspartic acid and 3-hydroxy-fatty acid residues by degradation experiments. The amino acid sequences of plusbacins A2 and B2 were confirmed by Edman degradation of their deacylated products, and supported by mass spectrometric studies. Fromthe above, structures of all componentsofplusbacins were concluded.