Conformation and Dimerization of Actinomycin-Related Peptide Lactones in Solution and in the Solid State

Article abstract of DOI:10.1021/ja00310a065

Actinomycin-related peptide lactone derivatives with the amino acid sequences Thr-D-Val-Pro-Sar-MeVal and Thr-D-Val-Pro-Sar-MeAla and the corresponding actinomycins (actinomycin D and its novel 5,5'-MeAla analoque) were synthesized by a new route.The solution properties of these compounds were studied by proton NMR in chloroform and acetone solutions.In dry chloroform, two conformers, A and C, are found, the ratio of which was concentration-dependent and results from dimerization of the A conformer.An X-ray crystallographic investigation of a Thr-D-Val-Pro-Sar-MeAla derivative indicated that hydrogen-bond associated pairs of A conformers, with a juxtapositional geometry remarkably similar to that known for actinomycin, were present in the solid state.