Helvecardins A and B, novel glycopeptide antibiotics. II. Structural elucidation

Helvecardins A and B, which are produced by Pseudonocardia compacta subsp. helvetica, are new members of glycopeptide antibiotics. They contain the same pseudoaglycone as beta-avoparcin and the same compositions of neutral sugar, amino sugar, and amino acid except that 2'-O-methylrhamnose was detected in helvecardins instead of rhamnose in beta-avoparcin, and mannose was not detected in helvecardin B. From these results and 1H NMR and mass spectral analyses, helvecardins A and B were determined beta-avoparcin 2'-O-methylated on rhamnose and demanosylhelvecardin A, respectively.