Different solution and solid-state conformations of the antibiotic cycloheximide

The ¹H NMR spectra of the antibiotic cycloheximide in CDCl₃ and CD₃OD have been assigned. Analyses of coupling constants and difference NOE spectra showed different conformations in these two solvents, due to changeover between intra- and inter-molecular hydrogen bonding. The twist boat cyclohexanone found in the solid state was not detected in solution. The results are compared with the solution and solid-state conformations of the antitumour agent sesbanimide A.