Structural investigation of the antibiotic ristomycin A. The amino acid constituents.

Abstract

Hydrolysis of the O-methylated aglycone of ristomycin A by a mixture of KOH and NaBH4 yielded a mixture of aromatic amino acids which, after N-acetylation and Ome.hylation, were separated by chromatography on silica gel. Compounds III' VII were isolated and identified by pmr and mass spectroscopy.Compounds V -VII were also oxiiatively degraded to the corresponding benzoate esters. Compounds III and IV are derived from ristomycinic acid (I) and V from actinoidinic acid (II), both of which had been obtained in earlier acid hydrolyses of the antibiotic.Compounds VI and VII had not been detected previously nor glycine which was also found to be a product of base hydrolysis. It is postulated that the new products arise from bisdechlorovancomycinic acid (X). It is concluded that aglycoristomycin A comprises I, II and X which also corstitute the aglycone of ristocetin A.

Actaplanin, new glycopeptide antibiotics produced by Actinoplanes missouriensis. The isolation and preliminary chemical characterization of actaplanin.

“…Several recent structural studies of glycopeptide antibiotics1~5) have shown that these antibiotics appear to hold several chemical features in common. Typically, glycopeptides give rise to an "aglycone," neutral sugars"') and an amino sugar upon mild hydrolysis', [1][2][3][4][5][6][7][8][9][10][11][12]. Furthermore, the aglycone is a complex peptide which retains the same amino acids present in the parent after total hydrolysis and also some of the antimicrobial activity of the parent.…”

Calcium(II) and the trivalent lanthanide ion complexes of the bleomycin antibiotics. Potentiometric, fluorescence and proton NMR studies

“…The fact that the magnitudes of the chemical shift perturbations induced by Pr(III) increase with increasing metal ion concentration indicates that the antibiotic is in fast exchange on the NMR chemical shift time scale between its free and complexed states. The chemical shift perturbations in the presence of paramagnetic ions can be expressed as -Act 4" ^+ (7) where Act is the complex formation shift and is diamagnetic in origin, Ac is the shift arising from the Fermi contact interaction, and Ad is the shift arising from the dipolar interaction. In the present system Act is negligible since the spectrum of Blenoxane is unaffected by the presence of a saturating concentration of (28) (a) J. Reuben, "Handbook on the Physics and Chemistry of the Rare Earths", Vol.…”