De novo structure determination of vancomycin aglycon using the anomalous scattering of chlorine

The crystal structure of vancomycin aglycon has been determined by exploiting the anomalous scattering of Cl atoms present within the molecule. Real-space-reciprocal-space cycling with Shake-and-Bake successfully located the chlorine positions from the Bijvoet differences, even though the anomalous difference Patterson map proved to be uninterpretable. The chlorine anomalous differences lacked sufficient phasing power to produce interpretable electron-density maps. However, when combined with high-resolution native data, the chlorine positions were sufficient to determine the structure using either Shake-and-Bake or a tangent-formula expansion.