Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment

Zervamicin IIB is a member of the α‐aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C‐ and 15N‐enriched peptaibol is described. This compound was isolated from the biomass of the fungus‐producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C,15N‐labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C,15N‐labelled minimal medium containing 13C‐methanol and 15N‐ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (>90%) and led to the complete 13C‐ and 15N‐NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1Hα, 13CO and 13Cα agrees well with the previously determined structure of zervamicin IIB in methanol solution. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.