Revision of the Absolute Configurations of Chelocardin and Amidochelocardin

Even with the aid of the available methods, the configurational assignment of natural products can be a challenging task that is prone to errors, and it sometimes needs to be corrected after total synthesis or single-crystal X-ray diffraction (XRD) analysis. Herein, the absolute configuration of amidochelocardin is revised using a combination of XRD, NMR spectroscopy, experimental ECD spectra, and time-dependent density-functional theory (TDDFT)-ECD calculations. As amidochelocardin was obtained via biosynthetic engineering of chelocardin, we propose the same absolute configuration for chelocardin based on the similar biosynthetic origins of the two compounds and result of TDDFT-ECD calculations. The evaluation of spectral data of two closely related analogues, 6-desmethyl-chelocardin and its semisynthetic derivative 1, also supports this conclusion.

Automated summary

The absolute configuration of amidochelocardin was revised using a combination of XRD, NMR spectroscopy, experimental ECD spectra, and TDDFT-ECD calculations. Based on the biosynthetic engineering of chelocardin and the results of TDDFT-ECD calculations, it is proposed that chelocardin has the same absolute configuration. The evaluation of spectral data of two related analogues further supports this conclusion.