Chalcomycin: Single-crystal X-ray crystallographic analysis; Biosynthetic and stereochemical correlations with other polyoxo macrolide antibiotics.

The stereochemistry of chalcomycin (1), a neutral 16-membered macrolide antibiotic, was established by X-ray crystallography. A correlation model for 16-membered macrolides (2), together with its biochemical rationale, is presented and applied to the configurational assignment of seven other analogous neutral macrolides (aldgamycins F, G, CP-61,884 complex, neutramycin, and swalpamycin). The chalcomycin molecule appears to be conformationally restrained in a rigid manner.