Biosynthesis of the boron-containing antibiotic aplasmomycin. Nuclear magnetic resonance analysis of aplasmomycin and desboroaplasmomycin.

Abstract

The 360 MHz 1H NMR spectra of the boron-containing macrolide antibiotic Aplasmomycin and of desboroaplasmomycin were analyzed to extract most of the parameters revealing the conformations of these compounds in CDCl3 solution. It was found than the conformation of aplasmomycin in CDCl3 solution is identical to that in the solid state and that removal of the boron atom from aplasmomycin results only in a slight conformational change of the molecule in CDCl3. All resonances observed in the 13C NMR spectrum of the antibiotic have been assigned on the basis of chemical shift theory, multiplicity analyses, single frequency proton decoupling experiments, comparison with several derivatives and model compounds, specific deuteration experiments, and analysis of one-bond carbon-carbon couplings of pairs of carbon atoms.