Structure of the Antibiotic OA-7653

Article abstract of DOI:10.1021/jo00238a002

The structure of the glycopeptide antibiotic OA-7653 is assigned as 2.Elucidation of the structure is based primarily on two-dimensional NMR experiments, analogies with other glycopeptide antibiotics of the vancomycin series, and selective degradation studies.Antibiotic OA-7653 contains a heptapeptide aglycon core in which the amino acids N,N-dimethylalanine and glutamine are encountered as a G and F components of this unit.Mild acid hydrolysis of the antibiotic effects the conversion of the δ-carboxamide of the glutamine residue to yield the carboxylic acid 3 in a reaction that is shown to proceed without rearrangement.This latter conversion to 3 proceeds without effecting cleavage of the β-glycosidic link between the aglycon and glucose.The ¹H spectra of OA-7653 and its derivatives in DMSO at pH 4.0 are shown to represent major and minor conformers that are exchanging at rates comparable to the NMR time scale.