OLIGOMYCIN-B AND OLIGOMYCIN-C - COMPLETE AB-INITIO ASSIGNMENTS OF THEIR H-1 AND C-13 NMR-SPECTRA AND A STUDY OF THEIR CONFORMATIONS IN SOLUTION

Self-consistent, full assignments of the H-1 and C-13 NMR spectra are reported for the macrocyclic antibiotics oligomycin-B and -C. Solution conformations, deduced from proton-proton and proton-carbon-13 coupli ng constants as well as from chemical shift considerations, are compar ed with X-ray data. While coupling data are compatible with a fair deg ree of similarity between the overall conformations in the solid and s olution states, small bur definite differences are apparent in the ''n orthern'' part of the macrocycle (C-6 to C-12) of oligomycin-B. On the other hand, conformational differences, relative to the same region, have been detected between oligomycin-B and oligomycin-C in solution; this is likely due to steric crowding between bulky substiuents at C-9 and C-12 in oligomycin-B. (C) 1998 Elsevier Science B.V. All rights r eserved.